Sheldon Cooper

Sheldon Lee "Shelly" Cooper, B.S., M.S., M.A., Ph.D., Sc.D., is a Caltech theoretical physicist who shares an apartment with his colleague and best friend, Leonard Hofstadter. Originally from East Texas, Sheldon started college at the age of 11, receiving his first Ph.D. at 16. Sheldon was involved in numerous experiments as a wunderkind, such as his plan to provide free electricity for his town by building a nuclear reactor - a plan stopped by government pen pushers claiming it's illegal to store yellowcake uranium in a garden shed! Unashamedly geeky, he has no qualms about speaking Klingon, wearing vintage t-shirts sporting superhero logos, or spouting various historical and cultural anecdotes (e.g., his account of the introduction of the fork into Thailand). While he might claim to be the perfect human specimen, Sheldon does have his faults. Sheldon is characterized by: a strict adherence to routine; an overtly intellectual personality; a tenuous understanding of irony, sarcasm and humor; and a general lack of humility or empathy, the former of which is demonstrated in the fact that he has no problem voicing to his peers his admiration for his superior intellect. These qualities, along with his penchant for pranks, are his character's main source of humor and occasionally cast him as the primary antagonist of the series. He has been described as the show's breakout character.

Early Life
Sheldon was born in Galveston, Texas to Mary Cooper, a devout Evangelical Christian, officiated at Lawrence Memorial Hospital though he actually "fell out" of her at a K-Mart. His father, George Cooper, was a Texan Homer Simpson who died quite a while ago due to an unknown cause. He has a twin sister named Missy and an older brother named George Jr., both described by their mother to be "dumb as soup." Sheldon was raised according to his mother's beliefs, e.g., learning how to pray and becoming the co-captain of the East Texan Christian Youth Holy Roller Bowling League Championship team, seven-to-twelve year-old division. Meanwhile, he was forced to watch football by his father.

Like the typical nerd, Sheldon was bullied a lot as a child, mainly by his classmates, neighborhood kids and his siblings. Not so much because of his looks, but because of his expressing intellectual superiority to them and being a complete Smart-Alec. He would get a lot of beatings from the neighbor kids and would get swirlies all the time, even in church. There were also noogies and wedgies. He would have some of his stuff taken away from time to time, like his lunch money or his kites. Luckily, he only had to cope with this until he was eleven, as he then went straight to college, but that didn't stop his siblings. Sheldon tells Amy Farrah Fowler, that his childhood was "hell." Further anecdotes reveal he built a so-called "Sonic Death Ray" that didn't even slow down the neighbor kids (all it did was piss off the dog), and constructed an armed robot, using homemade integrated circuits from ceramic semiconductor substrates cooked in his sister's Easy-Bake Oven which he modified, to defend his room from Missy (Missy got her eyebrows burned off as a result a malfunction).

Sheldon entered college at the age of eleven, right after completing the fifth grade. At age twelve, filled with disappointment at not receiving a titanium centrifuge to separate radioactive isotopes, he had to be flown to a hospital by helicopter to be treated for radiation damage following a mishap when he built a CAT scanner (which also resulted in the death of his sister's guinea pig, Snowball) and conducted experiments involving the height of stairs only to deduce that if a step on a staircase is two millimeters off or more, a person is likely to trip - his findings evidenced by his father breaking his clavicle. When Sheldon was thirteen, he attempted to build a nuclear reactor in order to provide free electricity for his town but it failed after a government agent informed him that it was illegal to store yellowcake uranium in a shed; he then had a big tantrum as a result. When Sheldon was fourteen years old, he graduated college summa cum laude, began graduate school, and was the youngest person at the time to receive the Stevenson Award at "fourteen and a half." He received his first doctorate at the age of sixteen and he then spent four years on his second dissertation, before obtaining his current job.

Career
Dr. Sheldon Cooper is a senior theoretical particle physicist at the California Institute of Technology, focusing on string theory and its alter ego M-theory. He has held this position for three-and-a-half years at the outset of the show. Previously, he was a visiting professor at the Heidelberg Institute in Germany at age fifteen and examined perturbative amplitudes in N=4 supersymmetric theories leading to a re-examination of the ultraviolet properties of multiloop N=8 supergravity using modern twistor theory at age sixteen. For his contributions to theoretical physics, he won a Caltech Chancellor's Award for Science.

Sheldon's work on string theory is concentrated in several different directions. Notably, Sheldon has refocused his research from bosonic string theory to heterotic string theory. He wrote a paper on the decays of highly excited massive string states and illustrated mirror symmetry in the footnote of a publication. He determined that three-dimensional string-nets provided a unified picture of fermions and gauge bosons and reconciled the black hole information paradox with his theory of string-network condensates following a breakthrough in showing how neutrinos emerge from a string-net condensate. He also designated time for solving the spacetime geometry in higher spin gravity and worked on time-dependent backgrounds in string theory, specifically quantum field theory in D-dimensional de Sitter space.

In "The Monopolar Expedition", Sheldon received a grant from the National Science Foundation to lead an expedition to the Magnetic North Pole in the Arctic Circle for an experiment in search of slow-moving magnetic monopoles, with Leonard, Raj and Howard as his support team. In the experiment, he detected what he believed was significant monopolar magnetic charge, validating one of the chief predictions of superstring theory. Though Sheldon publicly announced he had confirmed string theory and would receive a Nobel Prize, he learned that the charge detected was actually static electricity from the others' electric can opener, forcing Sheldon to issue a retraction to his announcement and severely damaging his reputation at the university. Soon after, National Public Radio with Ira Flatow from Science Friday interviewed him by phone from his office, regarding the recent so-called discovery of magnetic monopoles in spin ices.

Sheldon did work in quantum loop corrections, but he hadn't considered a Lorentz invariant field theory approach. However, he believes string theory better unites quantum mechanics with general relativity than does loop quantum gravity. He neither gives credence to the notion that quantized spacetime will manifest itself as minute differences in the speed of light for different colors (as he expects matter consists of tiny strings) nor that only loop quantum gravity calculates the entropy of black holes.

Sheldon's research spans particle cosmology and studies the interplay between particle physics and cosmology during the early history of the Universe. With Rajesh Koothrappali, he explored the string theory implications of gamma rays from dark matter annihilations and considered methods of optimizing a particle detector for 500 GeV particles to this end. At a San Francisco conference, Sheldon tried to initiate a collaboration with Nobel Prize-winning physicist George Smoot by presenting him his paper on astrophysical probes of M-theory effects in the early universe. The famous physicist Stephen Hawking reached out to him during a lecture stay at Caltech after Sheldon's brilliant mind was revealed in a reading of his fascinating, though wrong, paper positing that the Higgs boson is a black hole accelerating backwards through time. He also maintained a correspondence with cosmological physicist Elizabeth Plimpton for years about their mutual interest in gravitational wave signatures of inflatons in the early universe. When Caltech received a new open science grid computer, Sheldon attempted to schedule time to run simulations of structure formation in the early universe. However, he no longer preoccupies his time with investigating why the predicted mass of the quantum vacuum has little effect on the expansion of the universe.

Moreover, Sheldon is active in the field of particle physics phenomenology at high-energy colliders such as the LHC. Sheldon came close to figuring out why the Large Hadron Collider has yet to isolate the Higgs boson particle. Though, he was refused clearance for a very prestigious government research fellowship at a secret military supercollider, located beneath a fake agricultural station 12.5 miles southeast of Traverse City, Michigan.

Sheldon also engages in condensed matter physics research on occasion and has lectured on topological insulators, as well as given a seminar on thermodynamic fluctuations. With Leonard, he coauthored a paper entitled Paradoxical Moment-of-Inertia Changes Due to Putative Super-Solids, to be presented at an Institute for Experimental Physics topical conference on Bose-Einstein condensates. He discovered that electrons traveling through a graphene sheet on hexagonal pathways possess zero effective mass since they coincidentally exhibit the same dispersion pattern as fermions and must be considered as a wave. In addition, he had a minor epiphany regarding the polymer degradation phenomenon.

Sheldon has grappled with Gedankenexperiments (i.e., "thought experiments") to illustrate the quantum measurement problem. He produced four out of the five Gedankenexperiments he thought necessary for a cogent restatement of the quantum measurement problem, before the information was lost.

Characterization
Aside from his idiosyncrasies, obsessions, and extreme narcissism, Sheldon is logical. He possesses an eidetic memory and an IQ of 187, although he claims his IQ cannot be accurately measured by normal tests. Sheldon has an overly extensive general knowledge, such as shown by his comments regarding various details of anecdotal knowledge (for instance, about the introduction of the fork into Thailand).

Sheldon also has qualities associated with being a prodigy, such as an inflated ego, social ineptitude, and an inability to relate emotionally with others. Despite his intelligence, he has a distinct lack of emotional maturity and is often baffled by even the most common social interactions. He not only fails to understand the simplest sarcastic jokes made by Leonard, but also regards Penny's sadness over one of her breakups with blatant confusion.

However, recently, he has begun to understand the concept of sarcasm, attempting unsuccessfully to employ it himself towards Penny in the second season, and successfully employing it towards his friends in the third season. He appears to have a complete disinterest in romantic relationships, and his eccentricities, direct remarks, and demanding nature put him at odds with his own friends and especially Penny. Sheldon's expression of his more advanced intelligence has gotten him fired from his job, and even Leonard is surprised to learn that Sheldon is conceited enough to believe that Isaac Newton is intellectually inferior to himself. Sheldon hates it when someone stops him when he is trying to explain something. If this happens: a tic starts on his face until he can complete what he wants to say. He cannot and will not drive, and thus someone must always drive him. (Except when he drives Penny to the emergency room in "The Adhesive Duck Deficiency".)

He also has symptoms of obsessive compulsive personality disorder and Asperger's syndrome, e.g., when he finds Penny's apartment messy, he sneaks in during the night and cleans it up because he can't stand being in the same hallway with something so disastrous, he refuses to sit anywhere other than his designated spot on the couch and follow set routines, and the running gag of the show is that when he knocks on Penny's door, he has to say Penny's name every three knocks (he does this thrice everytime).

Sheldon occasionally uses slang (in a very unnatural fashion), and follows jokes with his catchphrase "Bazinga!". He is not entirely sure how to hug someone, and avoids human contact whenever possible. Despite his egocentricism, Sheldon appears to be somewhat aware of his social ineptitude, particularly his lack of understanding of sarcasm. He mentioned that he keeps a record of his daily conversations after Penny snapped at him and Leonard asked him why, to which he suggested that Leonard check his conversation records "to see if I messed up anywhere." Sheldon is also a difficult person to work with and generally displays apathy to the world around - in The Toast Derivation, Sheldon was revealed to have criticized Bill Gates for focusing on his charity work rather than Windows Vista, a remark that earned him a punch in the face.

Sheldon does show on rare occasion interest in relationships, which was most prominently seen with Amy Farrah Fowler. However, he does not express it directly, instead devoloping strange behavior patterns such as buying cats or refusing to open dicussion to the matter.

Childlike Qualities
Sheldon also possesses many childlike qualities. For example, even though he is unaware of it, Sheldon is extremely stubborn. Examples of this include naming the Caltech Physics Bowl team or deciding to go to San Francisco by train instead of flying (due to his fascination and love of trains), and his needing of his mother (or Penny) to care for him when he is sick, which involves singing "Soft Kitty" and rubbing Vicks on his chest. He cannot stand to be interrupted, concede when he doesn't know something, or hear people bicker or argue, crinkling his lips with intense frustration when any of these events occur. Sheldon has not attempted to obtain a driver's license (although he does possess a learner's permit), and needs his friends to drive him everywhere; he refuses the bus. He attempts to learn to drive on a simulator. However, he fails instantly. Sheldon's defense is that he is "too evolved" to perform plebeian tasks; driving.

In Season 5's "The Pulled Groin Extrapolation", Amy asked Leonard to attend a wedding with her. Leonard asked why she did not ask Sheldon to go instead. Amy answered that Sheldon behaved like a child the last time so he is out. After Amy left, Sheldon said in a sing-song tone to Leonard; "Heh heh, you have to go to a wedding!" as he was unwrapping his newly-bought toy train set, further emphasizing his childlike qualities.

However, the majority of these problems can be traced back to his root personality fault of stubbornness, which many fans believe is because of Aspergers and/or OCD.

Interests
Like his friends, he is scientifically inclined, and is fond of comic books, costumes, video games, and science fiction, specifically Battlestar Galatica, Doctor Who, Stargate, Star Trek, Star Wars, and Firefly, although he strongly dislikes Babylon 5. He has claimed to be an honorary graduate of Starfleet Academy, and is an avid fan of science officer Spock. Other favorite characters of his are Batman, The Flash and The Green Lantern.

He likes playing Halo every Wednesday and paintball on the weekend with his friends. He can also play the piano and theremin, and seems to be a very good Tuvan throat singer, but would be better if not for a part in the roommate agreement denying him practice.

Sheldon often wears vintage T-shirts adorned with superhero logos specific to the DC universe, among them the Flash, Superman, Aquaman, and the logos of the various Lantern Corps. He usually wears a long sleeve shirt underneath it along with plaid pants. Sheldon is tall and thin (setting him apart from his shorter colleagues), with Penny, and later Leonard, saying he looks like a giant praying mantis.

Drugs and Alcohol
With few exceptions, Sheldon refuses all drugs, including alcohol and caffeine, as a promise to his mother. In addition, when Penny mixed alcohol into his drink, he began to play the piano and sing To Life from the musical "Fiddler on the Roof" in front of an audience. A small amount of coffee made him extremely hyperactive, but unproductive in another. Taking valium also affected his behavior. Probably the most infamous time of him being drunk was when he had to give a speech in "The Pants Alternative" and he acted like a comedian due to the abundance of wine he drank to calm his nerves. The scene was uploaded on YouTube where it is revealed Sheldon also took off his pants and mooned the audience. Howard has once drugged him to get him to stop talking, but was unsucessful.

While it is argued that Sheldon drank beer in the Pilot, it is actually an orange soda (clearly seen when Leonard holds up his bottle in the hallway).

He does enjoy a Mountain Dew in "The Vengeance Formulation", one of the more caffeinated sodas, even calling it "refreshing". He also likes "diet virgin Cuba Libres", which is essentially a Diet Coke with a slice of lime and virgin Pina Collates. It appears that he can drink caffeinated beverages to a certain point, but not to the extent of coffee.

Softer Side
Despite his strange behavior, Sheldon has, at times, demonstrated a much softer side to himself. However, these moments are rather rare, and usually only reserved for those closest to him, such as Leonard, Penny, and Amy. Although his friendship with Leonard is usually strained because of Sheldon's quirky behavior and habits, Sheldon has called Leonard "his little buddy" or something of the sort on multiple occasions. He also shows an obvious unease whenever his friendship with Leonard is threatened. Sheldon has also showed friendly acts of caring towards Penny. In one instance, when Penny was low on money, Sheldon let her borrow a large amount of his savings, but while she worried about paying it back, he was entirely unconcerned as to when he got it back. Sheldon's willingness to lend money to others was later described by Leonard as "one of the few idiosyncrasies that doesn't make you want to, you know, kill him". Also, after Penny let him stay at her place when he locked himself out of his apartment, Sheldon sincerely thanked her for it. When Penny fell and dislocated her shoulder, Sheldon spent the entire night taking care of her, including driving her to the hospital despite the fact that he does not know how to drive. He finished the night by helping her into bed and singing soft kitty to her after she asked him too. He also hugged Penny again when she said she would talk to Leonard about having him take Sheldon to Switzerland rather than her. This prompted him to sincerely thank her and hug her. With the exception of his family, Penny, Wil Wheaton and Amy Farrah Fowler are the only people Sheldon have hugged. With the latter he specifically cuddled with in the episode The Isolation Permutation, after a discussion to console a weepy Amy who was craving human intimacy and physical contact. After turning down Amy's previous proposals of getting into bed together and french-kissing, Sheldon agreed with her final offer to cuddle, though he got upset over it later, by yelling at Leonard and Howard to keep Penny and Bernadette in line and have them apologize to Amy since consoling Amy had caused him to miss the time he had designated to solve Spacetime Geometry in Higher Spin Gravity and building his Lego Death Star. This particular event of him cuddling with Amy Farrah Fowler is a huge development of his personality since he is not shown to have much empathy or sympathy for others. His caring attitude towards Amy is also exemplified when he buys her a diamond tiara as a form of apology after having a fight regarding the importance of Amy's accomplishment when her research made the cover of a noteworthy science magazine. In another instance, Sheldon acted disrespectfully in Amy's laboratory when he was taking his required vaction time. The next day, however, he returns and after a few attempts, meekly apologizes to Amy, showing a vulnerable side of himself that isn't usually seen considering his egotistical attitude.

Religion
In contrast to his profoundly religious mother and devout Christian upbringing, Sheldon has no interest in religion - he tends to ignore or express dislike for religious celebrations such as Christmas, and wastes no time in bringing up the Pagan origins to each festival. Additionally, his scientific beliefs often come into conflict with the spiritual beliefs of his mother, Mary. Nevertheless, he has an agreement with his mother to attend church once a year, and once exclaims "Thank you, Jesus!" upon getting a strike in a bowling match against Wil Wheaton (his arch-enemy). His attitude towards God has been hinted at being of an Agnostic nature, when in the episode The Zarnecki Incursion he says "Why hast thou forsaken me deity whose existence I doubt..." Raj stated that one of the instance where Sheldon got food poisoning and he was "praying to the god he doesn't believe in to end it quickly".

Adherence to Laws
Sheldon also appears to have problems understanding societal laws at times. He is shown to drop objects out his window into traffic without regard, in addition to breaking into buildings. He has also been seen going into various places, such as a kid's play-area and working at the Cheesecake Factory, without being granted permission. He has expertise with picking locks and disarming alarm systems. Furthermore, the Department of Homeland Security notifies his mother when he acts contrary to federal law. As he states later, "Apparently, you can't hack into a top-secret government supercomputer and then try to buy uranium without the Department of Homeland Security tattling to your mother." This implies that Homeland Security is familiar with him, as instead of arresting and questioning him, they simply inform his mother and let her deal with him.

Traits
Though Sheldon has never been confirmed as having Asperger's syndrome, many of his traits and much of his behavior exemplifies it. These qualities include social ineptitude, a lack of empathy, obsessive–compulsive personality disorder, and many more traits which make him the most eccentric and bizarre of the characters in the show. Many of these traits are the reasons why Leonard finds him hard to live with and his friends find him so hard to be around. These include:


 * Mitosis: Howard jokingly believes Sheldon reproduces with mitosis. Leonard had a nightmare where Sheldon reproduced in this manner after the latter ate too much Thai Food.
 * Obsessive–compulsive personality disorder: Sheldon exhibits a strict adherence to routine, such as doing specific recreational activities on specific days of the week, going to the bathroom on a specific time every morning, eating specific food items on specific days, being unable to reconcile changes to food orders, doing laundry on a specific day and time (every Saturday night at 8:15), or knocking on the door a certain number of times while repeating the name of the person he is seeking with a particular frequency ("[knock knock knock] Penny [knock knock knock] Penny [knock knock knock] Penny" being the most common.) Amy Farrah Fowler notifies this to Sheldon as a symptom of Obsessive Compulsive Disorder and she finds he is in denial over it. Sheldon labels all home utensils, appliances, etc., including his label maker. He also makes loud noises (or musical notes with a xylophone) in every theater before a movie, attempting to locate the "acoustic sweet spot". However, he can adapt to seats with sub-optimal conditions, such as suitable cushion densities and light dispersion, provided he has the opportunity to test them.
 * Narcissistic personality disorder: Though not technically meeting all or enough requirements for a formal diagnosis, Sheldon constantly points out his superiority among his friends and belittles everyone all the time. Sheldon does not treat anyone as his equal and believes that only his ideas are right. As a result, he does not take suggestion. He also refuses to admit he did anything wrong, blaming it on trivial reasons.
 * Mysophobia: He is constantly worried about others touching his food, washes his hands as often as he can, and showers twice daily. Leonard used his concerns for food to mock him in "The Einstein Approximation", as did Raj in "The Engagement Reaction". Penny has stated that he still has not learned to not to insult those who handle his food, to which Amy Farrah Fowler agrees. For example, when Penny touched one of his onion rings and put it back, Sheldon threw out all of the onion rings, saying that she had "contaminated their integrity." However, he does not seem to do much when Penny implies that she spits on his hamburger at the Cheesecake Factory.
 * Ornithophobia: Sheldon has had horrible experiences with birds in his past, which has led to ornithophobia (a fear of birds). When Sheldon was a toddler, a hummingbird, which he describes as the vampire of the flower world, dived down into his stroller and tried to get at his apple juice in his sippy cup. When he was seven, his neighbour's chicken got loose and chased him up the big elm tree in front of his house. When he was twelve, a magpie tried to take his retainer out of his mouth and when he was 16, a parrot in the pet store window called him "fat ass". He finally overcame this fear after he was forced to confront a black-throated magpie jay.
 * Hypochondriasis: He is extremely worried about becoming sick. He became worried about Penny infecting him with influenza and subsequently contracted it. Another time, he wanted a full medical examination by Leonard's girlfriend, Dr. Stephanie Barnett, in order to discover the cause of a high-pitched noise in his head. This was later used aganist him by saying that he had an inflamed larynx and that he needed to stop talking immediately. When Howard's mother is sent to the hospital, Sheldon refuses to go due to exposure to pathogens and germs, until Penny confronts him. Though, he accidentally wanders into a biohazard room at the hospital, after fearing the restroom's cleanliness, and endures a two-week quarantine. Sheldon showers twice a day and washes his hands as often as he can. In addition, Sheldon has a red toothbrush that is kept in a Plexiglass case under a UV lamp.
 * Inability to lie: When Sheldon is complicit in a lie, he exhausts all of his efforts in his almost always unsuccessful attempt to make it believable. Similarly, he cannot be entrusted with a secret because he develops nervous tics. However, it is easier for him to lie if he has prior knowledge of the deception or an "ironclad alibi" thought out in advance, as opposed to it being "impromptu dishonesty". Penny taught him a way to lie using sarcasm.
 * Intolerance of people in his bedroom. One time, he was distraught when Penny entered his room in the middle of the night. On another occasion, Sheldon hesitantly let Penny in his bedroom to get a key for his desk to retrieve a USB flashdrive, constantly reminding her that, far from creating a permanent easement, it was only one-time permission.
 * Stage fright: While perfectly comfortable speaking to small groups, Sheldon cannot speak to crowds deemed large enough to trample him (36 adults or 70 children) without having a panic attack or fainting.

He also keeps a record of what he considers faux pas "strikes", which he allocates to those who violate his self-imposed conditions. Upon receiving three strikes, Sheldon gives them the choice of either apologizing, being "banished" from the apartment, or taking a "class". For many of the aforementioned characteristics, Sheldon's friends often consider him "insane" or "crazy" despite Sheldon's repetition of another catchphrase "I'm not insane/crazy! My mother had me tested." His mother later confirms this to Leonard; the doctor said he was sane, but she regreted not following up with a specialist in Houston. Despite Sheldon's personality disorders and difficult habits, his friends usually just do what he says because it is easier. It has also been revealed that Sheldon has a bifurcated uvula, something which he is self-conscious about.

Sheldon's Spot on the Couch
The most notable feature of Sheldon's obsessive-compulsive disorder is his refusal to sit anywhere other than his designated spot on the far left cushion of the couch in his apartment, which he considers his "single point of consistency in an ever-changing world" and "the singular location in space around which revolves my entire universe", exceeding his love for his mother. He describes his spot on the couch as being his point 0, 0, 0, 0 if his life were a Cartesian coordinate plan. Sheldon regularly reproaches Penny and other people for sitting in his spot. Even disruptions to this location are enough to disturb him. Although he did allow Penny to sit in his spot in the first episode, as well as Howard, for a short time in "The Apology Insufficiency", only 94 seconds later, he reclaims his spot. As well as his designated spot in the apartment, if Sheldon is ever in a different area where he is going to sit down, such as Penny's apartment, he has to choose the best sitting location based on such things as optimal television viewing, lighting, airflow, and cushion density. In "The Werewolf Transformation", when his barber was ill and chaos ruled his life, he didn't object to Penny sitting in his spot.

Quotes

 * "Bazinga!"
 * —Quote when he makes a joke
 * "(knock x 3) Penny! (knock x 3) Penny! (knock x 3) Penny!"
 * —Quote from various episodes whenever he knocks on the door of Penny's apartment.
 * "That's no reason to cry. One cries because one is sad. For example, I cry because others are stupid, and it makes me sad."
 * —Quote from The Gorilla Experiment
 * "On the contrary. I find the Grinch to be an engaging and relatable character, I was right with him right up until he succumbs to social convention and returns the presents and saves Christmas. What a buzzkill that was."
 * —Quote from The Maternal Congruence
 * "I'm attempting to view my work as a fleeting peripheral image so as to engage the superior colliculus of my brain."
 * —Quote from The Einstein Approximation
 * "How can someone think we're going to blow up the moon!?! That's a good question. "
 * —Quote from The Lunar Excitation
 * "WHEATON......................................................................................................!"
 * —Quote from various episodes, usually after Wheaton messes with him
 * "I am not crazy, my mother had me tested."
 * —Quote from various episodes, always said after someone calls him crazy.
 * "Put it on the backburner. Anyway, it occurs to me, if I ever did perfect a time machine, I’d just go into the past and give it to myself, thus eliminating the need for me to invent it in the first place."
 * —Quote from The Luminous Fish Effect
 * "My mother says when we deceive people for personal gain we make Jesus cry."
 * —Quote from The Classified Materials Turbulence

Leonard Hofstadter
Sheldon is the best friend of Leonard, as they live together and are accustomed to tolerating each other ever since Sheldon put out an ad for a roommate with a list of criteria to follow. Despite Sheldon sometimes making remarks to the contrary, he appreciates Leonard and assures Leonard that his friend will not die alone. He even once told Leonard that he platonically loves him, when Leonard had to face his old high-school bully, Jimmy Speckerman. When Penny asks Leonard why he deals with Sheldon, he explains that Sheldon has actually saved his neck a few times, such as when he stopped him from being incinerated by his own improperly formulated rocket fuel and didn't tell on him to the landlord, the police or the Department of Homeland Security. This incident also lead to the destruction of the elevator, as Sheldon had just enough time to put the explosive contents of the container into the elevator before it exploded. Leonard also, more than all of Sheldon's other friends understands him the most, as viewed in many scenes where when all hopes failed to get Sheldon to participate in something, Leonard will be the last resort to come up with something successful. When Penny and Sheldon had a spat due to Penny sitting in his spot and touching his food and later refused to apologize to him, which resulted her being banished from the apartment, Penny came up with her own set of revenge, including banishing Sheldon from the Cheesecake Factory and messing up with Sheldon's Laundry Night. When things got really ugly between the two, a fed up Leonard secretly gave Penny Sheldon's mother's number, telling her it is Sheldon's Kryptonite. The feud ended after that, with Sheldon, clueless to the fact that it was Leonard who helped Penny, told Penny that she played well. Another instance was when Penny tried her hands at opening her own business by selling Penny Blossoms. When they had to stay awake all night to help Penny meet her order, a sleepy Sheldon refused coffee and decided to head to bed instead, leaving the rest to finish up by themselves. A frustrated Penny looked on to Leonard to do something and Leonard did, by saying to Sheldon that without his insight and leadership this entire enterprise will surely fail, which prompted Sheldon to change his mind and drink coffee.

Penny
Despite Penny not being a knowledgeable person nor sharing many of the group's interests, and having constant fights with Sheldon in the early episodes, they became close friends, such as when Penny cares for Sheldon during illness or when Penny takes him in when he is locked out of his apartment while his friends are in Las Vegas. Sheldon returns the favor as he cares for Penny when she dislocates her shoulder. In all of these instances, the story line ends with one of them singing "Soft Kitty," a song Sheldon's mother used to sing to him when he was sick. On the one hand, Sheldon and Penny spend a lot of time getting on each other's nerves: Sheldon often mentions how uneducated or untidy Penny is, while Penny likes to irritate him by sitting in his spot, messing with food, and they once started a futile war (Penny blocked Sheldon from doing his laundry on his laundry day, and he responded by exposing her clothes and underwear outside the window). However, they also efficiently team up, for example to plan Leonard's birthday (Sheldon only participated when Penny blackmailed him into helping) or to develop Penny's "Penny Blossoms" business, singing along to sailors songs to motivate each other. They end up spending a lot of time together as two close friends to help each other and give each other advice (Penny helping to find a suit for Sheldon for an awards ceremony, or seeking Stan Lee's address for him because he couldn't meet him as the other members of the group did; Sheldon teaching Penny physics to help her in her relationship with Leonard). On a few occasions, they also appear to share a sort of intimacy that Sheldon doesn't have with anyone else: they both take care of each other when they don't feel well; they stayed together in the flat, cranky and grumpy, as they had both caught the flu after a hug they had exchanged; Sheldon has an immediate, very nervous and alarmed reaction when he hears Penny calling for his help from her flat; they sing together "Soft Kitty" as a round in a kind intimate moment; Sheldon adds an amused "Bazinga" to one of Penny's jokes, to which she replies with a tender "Hmm..." Often when Sheldon seeks advice or help from Penny he begins his request with "you're so good at...." one of her faults and ends up insulting her though she usually let's it pass with a "WTF" expression.

Sheldon acknowledges Penny as one of his closest friends (along with Leonard and Raj), while he considers that Howard is a "treasured acquaintance," though he has known him a lot longer than Penny. Also, when Penny and Leonard break up, Sheldon still considers Penny a friend and makes dinner plans, which he tries to hide when Howard informs him that it is inappropriate behavior and "bros come before ho's." He actually goes through a lot of trouble (hiding frozen hot dogs in his pants, confronting a huge threatening dog ... ) just to dine with her, though he's already been forced to eat a whole meal with the boys. In the end, Leonard and Penny in a way share custody of Sheldon, taking him to Disneyland and out to buy new shoes.

The interaction between Sheldon and Penny has been praised by critics. James Chamberlin of IGN wrote: "Cuoco and Parsons are great in their own right, but when put together, they truly shine." Matt Roush of TV Guide said that Sheldon and Penny's "scenes and episodes together are usually Big Bang at its best." Todd WanDerVerff of The A.V. Club wrote that they "made such an inspired odd coupling that at times, it seemed as though the entire show were about them" and their chemistry "has some of the rattle and rhythm of the great comedic duos".[73] Chuck Lorre stated that Sheldon and Penny have "become a natural comic pairing" and they "bounce off each other beautifully."

Rajesh Koothrappali
Sheldon and Raj's relationship is rather complicated. Sheldon once offered help to Koothrappali by giving him a job under his supervision, which Raj reluctantly accepted to save him from getting deported back to India. Raj is easily annoyed with much of Sheldon's antics, but has grown accustomed to them. Before the boys went with Sheldon on the Arctic Expedition, Raj explained to Howard that the reason he puts up with Sheldon is because of his religion; 3 months of suffering at the Arctic Circle with Sheldon would mean he (Raj) would be reborn in the next life as 'a well-hung billionaire with wings'. Raj, as much as he hates Sheldon's opinions on every certain situation and his behaviour, considers Sheldon as a good friend.

Howard Wolowitz
Sheldon and Howard's relationship is purely existent, albeit extremely complicated. Sheldon often makes fun of Howard for not having a Doctorate. In "The Apology Insufficiency", Sheldon angers Howard by revealing details to the FBI that prevent him from obtaining a much needed security clearance. Howard refuses to accept Sheldon's apology, until Sheldon gives Howard his spot on the couch, prompting Howard to forgive Sheldon. Howard, much like Raj and Leonard are quite unused to his inflated ego. On the other hand, he and Sheldon are shown to get along well - He tried to help Sheldon drive on a simulator he created, and did help with Howard's creations. Nevertheless, the relationship between the two has its ups and downs.

Wil Wheaton
Growing up, Sheldon idolized Wil Wheaton. Wesley Crusher, Wil Wheaton's character on Star Trek: The Next Generation, had an eidetic memory just like him. Sheldon was such a fan that in 1995, he travelled ten hours by bus to the fourth annual Dixie-Trek Convention in Jackson, Mississippi, wearing his Star Fleet Academy cadet uniform in order to meet Wil Wheaton and get him to autograph his mint in-package Wesley Crusher action figure. However, his arduous journey, during which he had to twice violate his personal rule against relieving himself on board a moving vehicle, was for naught; although advertised to appear, he did not show up. It was at that moment, he vowed eternal hatred for Wil Wheaton.

In "The Creepy Candy Coating Corollary," Sheldon entered a Mystic Warlords of Ka'a tournament with Raj at Stuart's comic book shop in hopes of battling Wheaton, and put his name on the sign-up sheet as "DIE WIL WHEATON DIE". During this tournament, Sheldon utters in Klingon to Wheaton from across the room, "Revenge is a dish best served cold." When Raj and Sheldon get to the final round, they must face Wil and Stuart. Sheldon explains logically what cards must be in Wheaton's hand and how he is able to beat them. After Sheldon informs Wheaton why he hates him, Wil claims his grandma had died, knowing that Sheldon shares a special bond with his grandmother and would empathize with this plight. Sheldon falls for the ruse and throws the game, only to learn shortly thereafter that he had lied, causing him to reaffirm Wheaton's status as his mortal enemy in a display of rage akin to Adm. Kirk's reaction towards Khan's threat of marooning him on Regula in the Star Trek II: The Wrath of Khan. His true reason for not showing up is revealed in "The Russian Rocket Reaction" -- he was on 'Hollywood Squares".

Wheaton messed with Sheldon in a bowling game in "The Wheaton Recurrence." During said game, Sheldon named his team "The Wesley Crushers". In this encounter, Wheaton also managed to cause Penny to break up with Leonard through guilt.

Wheaton appears again in "The 21-Second Excitation" at a showing of the movie, "Raiders of the Lost Ark," with 21 seconds of deleted footage. After Wheaton and his crew were allowed to cut in line by the security guard, Sheldon exclaimed with his impersonation of Patrick Stewart's accent, "As Captain Jean-Luc Picard once said, the line must be drawn here... THIS far, NO farther!" Wheaton later boasted about his great seats and told Sheldon to 'suck it' via Twitter. When Sheldon, Leonard, Raj and Howard were eventually denied entrance to the theater, Sheldon stole the film cans containing the footage, resulting in an angry mob led by Wheaton chasing the four out of the theater.

In "The Russian Rocket Reaction," Wheaton invited Leonard and Sheldon to his place for a party. Here, Wheaton gave Sheldon his last mint condition, autographed Wesley Crusher action figure. While Sheldon forgave and hugged Wil Wheaton, Brent Spiner (who played Data in Star Trek: Next Generation) approached them, saying he "hadn't seen one of these [Wesley Crusher Action Figures] in ages," and proceeded to take it away from Sheldon. After tearing the packaging, Spiner became Sheldon's new archenemy.

Romantic
Of all the main characters of the show, Sheldon is presumed to be asexual and has displayed the least interest in pursuing a sexual relationship with anyone. He tries to avoid all human physical and emotional contact. He has, however, had a few opportunities to "get it on" - maybe more opportunities than the other characters. Being true to his personality, though, he never seems to realize it. However, the introduction of Amy Farrah Fowler into the show has changed this aspect of him, at least slightly. Even though Amy used to be a girl, who was his friend, but not his girlfriend, and now is his girlfriend, she is the closest person who may be romantically-linked to Sheldon. Though, their relationship used to be nothing more than that of friends, or, as Sheldon put it, "a relationship of the minds".

Lalita Gupta
Lalita was arranged to be married to Raj. They went on a date together which gradually deteriorated as alcohol made him obnoxious. When Sheldon arrived at the bar, he thought she looked similar to an Indian fairytale princess from a bedtime story his mother used to read to him when he was sick. When he told her, she was flattered and ended up dumping Raj and going out for dinner with Sheldon. When he was asked about it the next day, he simply said that they ate and discussed dental hygiene. He didn't seem to realize that he technically was on a date with her and when Leonard asked him if he was going to see her again he looked puzzled said "why would I see her again?, I have a dentist".

Ramona Nowitzki
Ramona was a huge admirer of Sheldon and had an obvious crush on him, which he didn't seem to notice. In The Cooper-Nowitski Theorem, she asked him out for dinner and brought it to his apartment. After that, she began spending more and more time with him, haunting the apartment night and day walking around like the T-X terminator from ''Terminator 3: Rise of the Machines. She ''prevented Sheldon from doing anything recreational like playing Halo, paintball or watching Battlestar Galactica so he could focus on his work that he was so enamored with. Eventually, he made a breakthrough. When she suggested they share credit, he simply responded "Get out!", after which she angrily left.

Martha
When Raj brought Sheldon to a faculty mixer to act as wingman, they picked up a girl named Abby and her friend, Martha, brought them to Sheldon and Leonard's apartment and played Rock Band with them. While Abby and Raj hit it off, Martha became interested in Sheldon. The two enjoyed a few stimulating discussions together at their second meeting, during which Raj and Abby "[got] busy," Martha visited Sheldon's room in the middle of the night and asked to come in, hoping for sex. Misinterpreting this, Sheldon went to sleep in Leonard's room and left Martha alone in his. She apparently lost interest in him after that.

Amy Farrah Fowler
Sheldon first met Amy via a dating site where Howard and Raj sneakily set up an account for him in the season 3 final, "The Lunar Excitation". Eventually, they found a perfect match for him and agreed to meet her at a cafe. When they told Sheldon, he refused to do it, believing dating sites to be "hokum". However, he was blackmailed into doing it when Raj said he had hidden a dirty sock in his apartment and would not remove it unless Sheldon went on the date. When they arrived, Sheldon had doubts until he met Amy, who acted exactly like Sheldon. She only agreed to come on the date as she and her mother have an agreement that Amy would date at least once a year. Sheldon noticed they had a lot in common and bought her a beverage of tepid water. Raj and Howard regretted what they had done, with Howard saying, "Good God, what have we done?".

In the season 4 premiere, "The Robotic Manipulation," Sheldon reveals that he has been talking to Amy for four months online and via text messaging, after they first met. Penny is amazed that Sheldon has a girlfriend and Howard and Raj call Sheldon and Amy, "Shamy." Sheldon denies that Amy is his girlfriend and that they mainly talk about Sheldon's theoretical physics, Amy's neurobiology and the possibility of having a child together via in-vitro fertilization. Penny convinces Sheldon to go on a proper date with Amy first, before he actually decides to have a child. She eventually ends up on the date with them, as she had to drive them to the restaurant. While there, Penny tries to make conversation, but fails. After the subject of Sheldon's first date comes up, Sheldon calculates the number of men Penny would have dated. He ends up with 193, with 31 sexual encounters. Amy then asks if Penny feels like a "slut" and reveals that she has had 128 sexual encounters (if you include stimulation of the brain to induce orgasm). Eventually, Penny convinces Sheldon to not have a child with Amy after threatening to tell his mother since his highly-reglious mother would frown upon a test tube, surragated, out-of-wedlock grandchild.

In episode 3 of season 4, Amy and Sheldon break up for a period of time after an argument over whose field of science is more superior. This results in Sheldon buying a clowder of cats, which worries Leonard. So he calls Sheldon's mother, who is unusually surprised at what she sees with Sheldon. She then calls Amy and usesthe technique of reverse psychology which Leonard instantly picks up on, but Sheldon is completely oblivious to. She tells Sheldon that it was a good thing he and Amy broke up because they are completely incompatible. Sheldon is instantly offended, so to prove his mother wrong, he offers Amy to reconcile, which she agrees after a negotiation on the amount of responsibility Sheldon has to accept for the break up (Amy offered 80%, Sheldon countered with 40%, settling at 65%).Afterwards, Sheldon gives away $20 to anybody willing to adopt his cats.

In episode 5 of season 4, Amy requests Sheldon to meet her mother, which terrifies him and he tries many ways to avoid her, as he thinks she has fallen in love with him. However, Amy says that she only wants to be friends with Sheldon and wants to pretend to be Boyfriend/Girlfriend to please her mother so that she will be silent on that matter. Sheldon freaks out Amy's mother a bit, which is what Amy wanted him to be, when they tell her about their "fake" sex life. Her relationship with Sheldon is complex; it began as a purely intellectual friendship which consisted solely of text messaging, but, at some urging from Penny, develops into a platonic friendship with dynamics similar to a romantic relationship, although not sexually intimate.

They later pretend to have had a sexual encounter (the made-up details of which included Amy becoming pregnant) as an experiment to see how long it would take the gossip to spread throughout their social circle, which Sheldon notes was "less than 24 hours." In The Agreement Dissection, she became drunk during a "girl's night" with Penny and Bernadette, at which Sheldon was present to escape Priya, and danced with Sheldon, after which Sheldon walked her home. She invites him in and, after advising him on how to deal with Priya, flirts with and then kisses Sheldon to which he responds "Fascinating". After she throws up and passes out, Sheldon puts a towel under her head as a pillow and leaves (but before doing this he regulated Amy's kitchen timer, which was making him go crazy).

The next morning, a hungover Amy video-calls Sheldon, and he informs her of the kiss, and when Amy admits she is unsure where to go from there, they agree to pretend the entire events of the evening never occurred.

Later, she invites Leonard to a wedding, explaining that she'd invited Sheldon before, but he "acted like a child." She and Leonard end up having a rather good time, though by the end of the night he'd sprained his groin dancing the Hokey Pokey and she's convinced he's in love with her. However, when Leonard tells Sheldon about the night, the way he describes it makes it seem as though he and Amy had sex. Sheldon bops Leonard rather hard on the shoulder, and states very firmly that Amy is not Leonard's, leaving his friend totally confused.

In The Isolation Permutation, Amy got depressed after Penny and Bernadette went bridesmaid dress shopping without her and Sheldon ended up comforting her. First she asked for sex due to wanting physical intimacy and the couple made counter offers and settled with cuddling, something Sheldon was erelucant to do.

A recurring topic for discussion among audience of the show is whether Amy may be the first person that Sheldon may have developed romantic feelings for, though he himself may not have realized it yet. It is clear that Amy is attracted to Sheldon, as witnessed in her many attempts to have some form of physical contact with him, such as kissing him while she was drunk, holding his hands and said that it was an experiment, and during the counter offers, she attempted to get Sheldon to agree to get into bed with her and french-kissing. Amy had also, in a scene in Season 5's "The Pulled Groin Extrapolation", told Leonard at a wedding that he has "a kinda-sorta-boyfriend playing with a model train and you don't hear me bitching about it", a clear reference to Sheldon. In "The Ornitophobia Diffusion", when Sheldon finally overcame his fear of birds and appeared infatuated by the bird, to the point he called him his little "Lovey-dovey". A slightly jealous Amy replied "guess you gotta have hollow bones to get some sugar around here".

Sheldon, while his feelings for Amy remains ambiguous, clearly cares for her at least. In "The Isolation Permutation", several events highlighted his care for Amy. When a devastated Amy wanted to be alone and did not respond to any form of communications Sheldon attempted to reach her, Sheldon grew worried and distracted, till Leonard suggested that they go over to her place to check up on her. While getting ready to leave their apartment, Sheldon shared news that a bob cat was spotted near Amy's place and Leonard responded that he does not think that Amy has been eaten by a bob cat. A shocked Sheldon said that he was only sharing a piece of news and now, thanks to Leonard, he is worried whether Amy has indeed been eaten by a bob cat. Later, at Amy's apartment, when she told Sheldon that she wanted to be left alone, Sheldon asked, rather awkwardly whether Amy would like to talk about what's troubling her, though he did add that he has no problem if Amy says no. Afterwards, when Amy counter offered with him regarding human intimacy and physical contact, Sheldon eventually agreed to cuddle with her. When a drunk Amy called Sheldon as he was building his Lego Death Star, he and Leonard went to see her at the parking lot near the licquor store when she called Leonard "Lil' Leonard" and Sheldon "Cuddles", a term which earned a frown from Leonard. Sheldon quickly retorted with "Yes Cuddles, we cuddled, grow up Leonard", showing that he no longer cares about what his friends may say regarding his relationship with Amy.

In "The Flaming Spittoon Acquisition", Sheldon at first claimed he was fine with Stuart asking Amy out on a date. But later, when he went to the comic book store with Leonard to return Leonard's Wild West and Witches expansion pack and found that someone else has replaced Stuart since he is out for coffee with Amy, he started feeling jealous. Leonard asked him whether he was okay but his reassurance on the matter looked doubtful. At the university cafetaria, as the guys were discussing the Wild West and Witches deluxe set, Sheldon was checking Stuart's Facebook page, and the guys were surprised to see that he has actually friended Stuart. Raj suggested that he did so just to keep tabs on Stuart's date with Amy. Leonard told him to acknowledge his feelings for Amy while Howard told him to challenge Stuart to a fight. Sheldon said that he could not care less about the date but ended up unfriending all three of them. Later, he went to Penny's apartment and asked Penny out on a date, to signal that he did not care about Amy and Stuart. When Penny told him that he only wanted to do so to make Amy jealous, he denied and wondered why everyone else is obsessed with Amy and Stuart and added whether those two have more pumpkin lattes or will have intercourse, showing that he did keep himself updated with the details of their date(s). Penny told him to buck up and talk to Amy.

Sheldon ended up interrupting Amy and Stuart's date at the movie by going into the movie they were watching and sitting next to Amy. When Amy asked what he was doing there, he covered up by saying that the thought of Amy sitting in a darkened theatre with a character like Stuart is repellant. Amy apologized and influenced him to man up to his feelings by saying that their current relationship status allows her to be in any repellant situation she likes. This was when Sheldon decided to propose an alteration to their relationship paradigm by saying he would no longer object if they characterize her as his girlfriend, but other than that nothing will change in terms of physical or otherwise. Amy pushed Sheldon to try saying that again without the negative but he refused so she provoked him by sliding towards Stuart and saying hi to him, following which Sheldon relented and asked properly if Amy is willing to be his girlfriend. She agreed and he left immediately. Later on, Sheldon waited inside Amy's apartment as she finishes her date. When Amy and Stuart was conversing outside her apartment, Sheldon told them to quickly wrap things up and when Amy and Stuart gave each other a friendly hug, Sheldon immediately retaliated by asking Stuart to take the hint that Amy has said goodnight. When Amy asked him how he entered her apartment, he complained whether she will keep nagging like this now that she is his girlfriend and introduced her to the Relationship Agreement. Amy did not seem to like the agreement although she said it is romantic. Sheldon told her she could get herself a lawyer. Amy agreed to the agreement anyway. As of now, the two have officially become a couple.

In "The Beta Test Initiation", Amy helped Sheldon with his YouTube series on vexillology entitled "Fun with Flags". At the beginning, she even made a suggestion which he described as brilliant, which was highly unusual since he normally dismisses other people's comments about his work. In one episode where Sheldon was describing the Bavarian flag, he even dressed up as a Bavarian and made Amy dressed up as a pretzel.

In "The Friendship Contraction", Sheldon asked Amy to take him to the dentist after all of his other friends refused, and Leonard had signed the clause on The Roommate Agreement to reduce his and Sheldon's relationship to mere acquaintances. However, Amy was busy with work and could not drive him. He tried to make her guilty by telling her that as his girlfriend, she had to cater to his needs, and even to the extent of asking her "where has the magic gone?". Amy looked upset at his comments and Penny ended up defending her.

In "The Vacation Solution", Sheldon decided to work at Amy's laboratory with her for a week, after he was forced to undergo his mandatory vacation. Once there, he was appalled by the tasks Amy told him to do, which were menial given his standards, such as washing the beakers and counting spores. Surprisingly, he could not accomplish any of the tasks right. Eventually, he confronted her on the matter. Amy reasoned that even if he was a genius, she could not assign him difficult tasks because he had no experience working in Biology. Sheldon retaliated by telling her that she was just afraid that he would be better than her. Annoyed, Amy let him slice the brain specimen she was working on. He ended up cutting his thumb and fainted at the sight of his own blood. After talking to Penny, Sheldon went back to apologize to Amy for his behavior, however, being Sheldon, he could not offer a sincere and direct apology. Amy downright refused to accept anything but a real apology so finally, he managed to mutter up a short "sorry". Amy accepted and told him to start washing the beakers again.

In "The Werewolf Transformation", Sheldon missed out on his regular haircut schedule, due to his regular barber being hospitalized. This event affected his daily routine because he could not get over not getting his haircut on time. When he was over at Amy's apartment, on their scheduled "girlfriend-boyfriend sing-a-long night", he could not concentrate. Amy suggested he go to Supercuts but he refused, equating Supercuts to "Sodom and Gomorrah with mousse". She then suggested he grew out his hair, because she thought he would look sexy with long hair. He refused to that as well. Later, Sheldon spiralled even more out of control by playing bongos at 3 a.m. and went to her apartment. The next day, when Leonard and Penny came over to pick him up, Amy revealed that she initially thought Sheldon's presence last night was a musical booty call. Sheldon finally relented to have his hair cut by Penny, after Amy convinced him by saying that there was no hair on her body she would not let Penny trim.

In "The Weekend Vortex", Sheldon agreed to go to Amy's Aunt Flora's 93rd birthday party. He began to have doubts on going after the guys told him that they would be having a 48-hour Star Ward online gaming marathon, like in the old days. He tried to persuade Amy to let him stay instead but she refused, saying that she followed all his protocols in The Relationship Agreement". Sheldon gave in, albeit forcefully. The next day, when they were about to begin their journey, Amy discovered that Sheldon had brought along his laptop with him. Sheldon told her that he had found a way to compromise, by being physically present at her aunt's party, but virtually present for the online gaming. Amy told him that it would make him appear rude since her family would want to talk to him. He told her that he will have his headset on so that he could not hear them in the first place. Upset, Amy sarcastically told him that if gaming was more important to him than his commitments to her, he could stay. He did not get her meaning and opted to stay. Amy was later seen upset and having gone to the party alone. She confided in Penny and Penny persuaded her to make a scene. The girls later barged into Sheldon and Leonard's apartment, while they were still gaming. Amy told Sheldon that she was going to embarrass him in front of his friends. She told him that she was leaving him for Arman, the miniature horse breeder. He asked her who Arman was but she tripped up on her words and failed to continue the ruse. Penny helped by telling Sheldon he hurt her by backing out on his words. Sheldon finally understood, and offered her Cooper Coupons to make it up back.

Sheldon's Family
Sheldon is very different from the rest of his family. His mother Mary Cooper is a devout Christian and a loving parent, and is one of the few people who refer to him as "Shelly". Leonard Hofstadter called her Sheldon's "Kryptonite" and will often call her when Sheldon is having serious issues.

Sheldon also has a fraternal twin sister, Missy Cooper, a hostess at Fuddruckers. Tall and attractive, she caught the attention of Leonard, as well as of Raj and Howard. Sheldon believes that within Missy's eggs lays the potential for another "superior mutation" like himself, and on this grounds considered his friends unsuitable to be with his sister. Sheldon became offended when he found that Missy tells others he is a rocket scientist; he apparently thinks the title is inaccurate and below him, telling her she might as well say he is a toll collector at the Golden Gate Bridge.

Along with Missy, Sheldon also had an older brother, named George Jr. who often beat him up, along with Missy. Mary described the two of them as being "dumb as soup." George Jr. has never been shown on the show.

Sheldon's father, George, an almost-redneck Texan Homer Simpson, died shortly before the series began, and Missy visited Sheldon to bring paperwork regarding their father's estate. Sheldon recalls that his father would force him to watch football ever since he was four despite his lack of interest for the sport. He also taught him archery which gives Sheldon an odd smell of K-Mart bourbon whenever he plays it, including the Wii version.

Sheldon is also very close to his grandmother, whom he calls "Meemaw," who in turn calls him "Moon Pie" Her name is not yet revealed so far.

Sheldon has a maternal uncle, Edward, who is called "Stumpy" as the result of a time when he cleaned a woodchipper by hand. Sheldon had another uncle, called Carl Cooper, who was killed by a badger while cleaning a chimney.

Sheldon's eating habits
Consistent with his characterization, Sheldon has many detailed and routine eating habits. He prefers his chicken diced, not shredded with low sodium soy sauce and spicy hot mustard, also brown rice instead of white. He loves to eat at Big Boy, an American restaurant chain, but eats at the Cheesecake Factory on Tuesday nights (presumably before the occasional Klingon Boggle game), which replaces eating at Big Boy (which then moved to Thursday until they had pizza on that day. Sheldon most likely eats at Big Boy whenever, or on special occasions.) Sheldon eats Giacomo's pizza on Thursday with sausage, mushrooms, and light olives. In The Agreement Dissection, however, Sheldon mentions that they used to order from a restaurant called Franconi's, which went out of business, forcing them to switch to Graziano's. Sheldon sorts his cereal numerically by fiber content, and rewards himself with "Honey Puffs" cereal.

Sheldon neither drinks coffee, nor alcohol, because he promised his mother that he wouldn't start doing drugs while he resided in California. Instead he likes drinking Diet Coke®. When forced to order a cocktail, Sheldon solves the problem by ordering a "virgin Cuba Libre," which is nothing more than a Coke® in a tall glass, served with a lime wedge. He then goes on to ask if Penny would make it diet. Sheldon likes Chinese food, and is adamant that the number of dumplings can be evenly split between all partakers of the meal, and always wants it from the restaurant Szechuan Palace. Sheldon even learns Mandarin to confront the restaurant when he believes they have been passing off orange chicken as tangerine chicken.

Sheldon eats Thai food on Mondays - Mee Krob with extra peanuts. Sheldon thinks chocolate pudding is the best type of pudding, and does not believe that three-tined forks are, in actuality, forks, but tridents, and refuses to eat with them. Sheldon doesn't like to go to the cinema if he can't eat Red Vines or drink Icees during the movie, and only if someone comes with him, so that he/she can give him the Heimlich Maneuver in case he chokes on popcorn. On the matter of Icees and Slurpees, Sheldon maintains that the two are wholly different. Sheldon always eats oatmeal for breakfast on Mondays, and always has French Toast for breakfast on certain days. Sheldon drinks herbal tea, sometimes with honey. His favorite flavor appears to be chamomile. Sheldon drinks hot chocolate only in the months containing the letter "R" (January, February, March, April, September, October, November, December) explaining "What is life without whimsy." Sheldon dislikes haggis and blood pudding. Sheldon believes that real Chili isn't supposed to have beans in it. Like Leonard, Sheldon hates Greek food, saying lamb kebab is "little cubes of charred meat that tastes like sweat".

Routines
Sheldon has many routines which he follows strictly. His morning routine is to wake up at 6:15 every Saturday, he pours himself a bowl of cereal, adds a 1/4 cup of 2% milk, sits down in his spot on the couch and turns on BBC America and watches Doctor Who. If he cannot complete this routine for some reason, he becomes very distraught. In addition, Sheldon goes to the Comic Book Store every Wednesday so he can see all the new comics on "New Comic Book Day." Also, every Wednesday night is "Halo Night", and Sheldon makes a big fuss about not starting at exactly 8:00pm and he must have the exact amount of time to play the game or else he takes the time out of eating or bathroom time. Sheldon does his laundry every Saturday night at 8.15 p.m. and uses a FlipFold to fold his t-shirts and socks. Each day, Sheldon has a specific pajama to wear. In the case of a stain, he still would not swap a pajama. He would rather sleep without bottoms as seen in The Barbarian Sublimation, when he spilled grape juice on his bottoms. Sheldon hates it when people change the contrast of the TV settings, talk to him through the bathroom door, change Band-Aids in front of him, buy generic ketchup, forget to rinse the sink, adjust the thermostat, or cook with Cilantro and mock trains.

Technology preferences
Being a scientific genius, Sheldon is very particular about his technological devices. Early on in the series, he uses what seems to be a customized Dell XPS M1710. After being robbed, he adopts an Alienware M17x Nebula Red laptop that runs on Windows 7, which he doesn't like as it is more user friendly than Window Vista. Sheldon's favorite Linux-based Operating System is Ubuntu. Sheldon has an iPhone 4, and he and his friends enjoy making fun of the Apple Genius Bar employees. He is also shown to use a Macbook Pro, with a red case, when video chatting to Amy Farrah Fowler.

Video Games
Sheldon and his friends play Age of Conan where he is a Conqueror by the name of Sheldor the Conqueror and has reached Level 80. Sheldon and all of his friends play numerous multiplayer online games; he is a Blood Elf Warlock (though it is originally stated he is a Night Elf Rogue) in World of Warcraft, loves Super Mario Bros. (wanting to control people in the same way he can control Mario in the video game Super Mario 64), and plays Halo every Wednesday night with his friends. He also plays bass guitar in the video game Rock Band. When Sheldon plays Wii archery, he likes to do it like in real life, including drawing an arrow out of a quiver because he believes the people at Nintendo can go so far as to help people recreate an actual athletic experience and they need to do their part too. Sheldon is not good at Mario Kart on Wii. Raj points out, that in real life or in games, he cannot drive. Sheldon is, however, very good at bowling on Wii Sports (and in real life). Sheldon likes to play the vintage text adventure "Zork".

Trivia

 * Sheldon is 31 years old. In The Russian Rocket Reaction, he reveals he was 9 years old when he started his all-time enemies list on a 1989 floppy disk. This age is further supported by Leonard's comment that Sheldon has been emotionally stuck for about 29 years in The Einstein Approximation.
 * According to Mary Cooper (Sheldon's Mother), Sheldon has her eyes, but has his daddy's temper and all that science stuff comes from Jesus.
 * According to Sheldon, he says that his mom wants grandchildren from Sheldon, but Penny adds that she wouldn't want a test tube grandson born out of wedlock (this being against her born-again religious beliefs).
 * Mary's waters broke for Sheldon and Missy in a K-Mart.
 * Sheldon was raised in a Christian household in Galveston, East Texas, Texas, USA (Texas just happens to be the same state that Jim Parsons was actually born in), although he once said his mom had to help his dad during tornado season, as the aluminum house he had slipped off its cinder blocks. (This could have been his father's way of a tornado shelter or his parents divorced by then and he moved into an aluminum trailer. The reason for these explanations being as we saw Sheldon's childhood home in the season 3 premier, where his mother still lives.)
 * Sheldon has perfected "glow-in-the-dark Fish"
 * Sheldon has 212 friends on MySpace.
 * Sheldon is allergic to bees and cats and gets asthma when he is around them (despite having a pet cat as a child and a whole glaring of cats when he missed Amy.)
 * Sheldon considers himself to be the first "Homo novus" - a new, evolved species of homo sapiens.
 * Sheldon doesn't believe in luck or coincidence, instead citing the Law of Large Numbers (LLN) in statistics as the explanation for such phenomena.
 * Sheldon was humiliated on National Radio during NPR's Science Friday with Ira Flatow when his voice became extremely high pitched due to Helium seeping into his office as part of a prank by Barry Kripke.
 * Sheldon agrees with the theory that 75-80% of any Rock-Paper-Scissors games you play with a person you are familiar with end up in a tie, and accordingly he prefers the variation Rock-Paper-Scissors-Lizard-Spock.
 * Sheldon used a Doppler Effect costume for Halloween.
 * Sheldon uses his Green Lantern action figure as a safe place for his emergency money.
 * Sheldon is fluent in Morse code.
 * Sheldon's favorite amino acid is Lysine, which is a major plot point to control the dinosaurs in the novel/movie Jussiac Park.
 * Sheldon thinks that his very strong attention to hygiene and his skill in writing Java Applets are the main reasons why his friends like him.
 * Sheldon loves trains and monkeys.
 * Sheldon fears dogs and formally, birds.
 * Sheldon had a cat named Lucky when he was a child, and this cat died because it was hit by a car. According to Leonard, this is another example of Sheldon's inability to understand irony.
 * Sheldon learned how to swim (on the floor) online.
 * Sheldon cannot stand whistling.
 * Sheldon thought about creating a Griffin when he was a child, after the family cat died. But his parents didn't want to secure the appropriate Eagle eggs and Lion semen.
 * Sheldon was very busy in his teenage years examining the range of diffusion in the supersymmetric theories, which brought him to re-examine the ultraviolet properties of supergravity a loop.
 * Sheldon's expenses account for 46.9% of his after-tax income.
 * Sheldon imposes and teaches behavior lessons to any friend of his who disappoints him for 3 consecutive times.
 * Sheldon thrives off his work, and if left jobless he loses all focus and moves onto a new experiment/obsession every day, much to Leonard's dismay.
 * Sheldon does not like teddy bears because he thinks bears are terrifying.
 * Sheldon was called by Leonard "one lab accident away from becoming a super villain".
 * Sheldon loves having his brain scanned.
 * Sheldon hates when people pronounce the "t" in often.
 * Sheldon only shows genuine affection for one person, his grandmother (or Meemaw), whom he writes to.
 * Sheldon is a Taurus, placing his birthday between 21 April and 20 May.
 * Sheldon, though unwilling to fight, is physically the strongest of the group, easily holding his own against Raj in an arm wrestle, and once referred to Leonard and Howard as 'tiny tiny men'.
 * Sheldon's little toes and lateral incisors are degenerated, which he says is due to his high level of evolution which keeps him from using a motor vehicle.
 * Sheldon once took a bet with Howard about a species of cricket, but lost and had to give Howard his Flash comic book.
 * Sheldon went to a Science Fiction convention on a bus for 10 hours and violated his personal rule of not urinating on buses twice to see Wil Wheaton, who didn't show up at the convention, which was revealed in season 5, that it was because Wheaton thought it be cooler to play on Hollywood Squares. This and the events of the card tournament and bowling alley, led Sheldon to consider Wheaton his arch nemesis. He has made three websites dedicated to hating him: wilwheatonstinks.com, .org and .net.
 * Sheldon has actually been kind to Penny; in two episodes he actually drove her to the hospital because she dislocated her shoulder, and loaned her a significant amount of money to help her in a financial pinch. (Even though this led Penny to think everyone was drilling her on her financial situation, even when they weren't.)
 * Sheldon was once offered a position at a secret military base, but was later forced to deny the position due to his inability to keep secrets.
 * Sheldon thought that the trip he and his friends took to the North Pole in Season 2/3 was "a hoot and a half."
 * It was mentioned that Sheldon and Leonard once had (before they were robbed) "A TV, 2 laptops, 4 external hard drives, a PS2, PS3, Xbox, Xbox 360, a classic Nintendo, a Super Nintendo, a Nintendo 64, a Nintendo Wii, Halo 1-3, Call of Duty 1-3, Rock Band 1-2, Final Fantasy 1-9, Legend of Zelda, Legend of Zelda: Ocarina of Time, Legend of Zelda: Twilight Princess, Super Mario Bros., Super Mario Galaxy, Mario and Sonic at the Winter Olympics, and Ms. Pac-Man. They also own Grand Theft Auto and Red Dead Redemption by Rockstar Games. They then probably got all the games and consoles again with a new T.V. and new computers. Sheldon's data was safe as well, as he was performing a backup in the previous episode. His new computer came with Windows 7 which he doesn't like because it's much more user friendly than Windows Vista.
 * Sheldon has adhesive whimsical duck stickers, holding umbrellas in his bathtub to prevent slipping.
 * Sheldon keeps a daily log of social interactions called Sheldon's Log ( in place of Captain's Log)
 * Sheldon doesn't trust banks because he believes that ATM machines will lead the charge of the robot armies when they revolt against humans.
 * Sheldon keeps Band-Aids with him at all times, as well as in his kitchen, top desk drawer, etc.
 * As of The Excelsior Acquisition, Sheldon has a restraining order from Stan Lee as well as Leonard Nimoy. In The Vacation Solution, he also mentions having one from the late Carl Sagan.
 * Sheldon has an in depth knowledge of American Football, since he was raised in Texas and his father would force him to watch it from the time he was four until he went off to college—the longest 7 years of Sheldon's life.
 * Sheldon rarely laughs, but when he does, it is a quick internal breath while showing a small smile. One of the rare times we hear him laugh properly is in season 5's "The Vacation Solution " over a physics mablib. Another time, he has laughed like that is when Leonard made a multiplication error in his work and that mistake was published.
 * Sheldon has never worn a shirt with words, unless a shirt logo has words on it, like in episode 5 of season 4, and always wears a long sleeved shirt under a t-shirt
 * Sheldon got drunk two times during the series: at the end of The Grasshopper Experiment and in The Pants Alternative and in the last, he showed a sense of humour and irony above what he normally has.
 * Sheldon apparently believes in the possibility of time travel to the past according to the beginning of The Luminous Fish Effect, explanations of time paradoxes in The Nerdvana Annihilation and a point of the room-mate agreement in The Staircase Implementation.
 * When somebody is distressed, Sheldon consoles them by saying "There, there"- only proof of his compassion towards other fellow human beings.
 * Sheldon is scared of waking Penny before 11 am., because she has a "I'll punch you in the throat" rule if he does.
 * Sheldon is skilled in weaving as he is seen weaving ponchos in his apartment.
 * If nothing is approved by Sheldon, he will not go through with it. (This is seen when Leonard, Raj, Howard, and Sheldon are trying to figure out the best way to see a movie. With Sheldon not approving any ideas, the rest leave him and he responds: "They're right. That was the only way.")
 * Prevening - Sheldon's made up word for the hours too late for Afternoon, but too early for evening.
 * Leonard had to surpass 3 barriers set by Sheldon in order to live with him.
 * Sheldon prefers the word "Hokum" to Bogus, Hocus Pocus, Mumbo Jumbo and Hokie Pokie.
 * He considers Amy Farrah Fowler a friend who is a girl, but not his girlfriend. This statement, however, is moot since The Flaming Spittoon Acquisition when the two officially become a couple.
 * He missed getting Stan Lee to autograph his comic since he had to go to traffic court to pay a fine, but ended up in jail after he insulted the judge and refused to apologise. He then went to his house with Penny and ended up with a restraining order against him.
 * Sheldon had built a robot called Shelbot, but was eventually discarded since Penny and Leonard were quite annoyed at Sheldon's idea for doing so.
 * Sheldon owns a Flash costume which he, so far, has worn on three occasions: in The Middle Earth Paradigm before Penny's Halloween party before switching to a Doppler Effect patterned suit, in The Work Song Nanocluster when high on caffeine and in The Justice League Recombination when attending a New Year's Eve costume party.
 * Prior to Sheldon's date with Amy in The Robotic Manipulation, the closest he had ever come to a such was "a semi-incestuous Teens for Jesus Fourth of July Hoedown" at which he square-danced with his twin sister, Missy.
 * Sheldon once attempted to declare his and Leonard's apartment a sovereign state and even made some currency for it. This was around the time Sheldon got fired from the university and he kept changing obsessions.
 * Sheldon hates dirty socks. This is demonstrated by the time that Leonard, Raj, and Howard signed Sheldon up on a dating site and the site found Sheldon's perfect match, but Sheldon refused to go until Raj told him that he put a dirty sock in his apartment and would not remove it unless Sheldon went on the date.
 * According to Sheldon in a deleted scene/blooper in "The Maternal Capacitance", the last time his mother visited, she tried to trick him into getting re-baptized below the Santa Monica Pier.
 * Sheldon went to Johnson Elementary School until he went to college at age 11. It was there he earned the nickname, "Smelly Pooper" with kids going around saying, "Shelly Cooper is a Smelly Pooper". Amy Farrah Fowler believes this is gold for gossip.
 * When Sheldon was under Howard's Mom's valium, he revealed that his mother used to smoke in the car. While Jesus said it was OK, they couldn't tell their dad, George.
 * Due to his good archery skills taught by his father, George, Sheldon believes he would have made a great elf.
 * There are two pieces of tape on the floor in Leonard and Sheldon's bathroom. One is in front of the sink and people must brush and floss their teeth from behind this piece of tape. A second piece is in front of the toilet for those that stand up to pee, though what exactly it marks was not specified. If someone gets the mirror or floor dirty, before Sheldon's inspection, they can lose their T.V. privileges.
 * As part of the roommate agreement created by Sheldon, Leonard has to wash his feet in a special tub before he gets in the bath or shower.
 * The tentative title for his future autobiography is You're Welcome, Mankind.
 * He had a Somalian pen pal who was kidnapped by pirates.
 * Sheldon has to be knocked out by an anesthetic when he goes for a cleaning at the dentist, as he bites.
 * In 1998, Sheldon bought a Tamagochi(sp) and it is still alive.

Gallery
Sheldon Cooper Sheldon Cooper