Leonard Hofstadter

Leonard Leakey Hofstadter, Ph.D., is an experimental physicist at the California Institute of Technology who rooms with Sheldon Cooper in apartment 4A of their rundown apartment building. Originally from New Jersey, Leonard was twenty-four years old when he received his doctorate and a Dissertation of the Year award for experimental particle physics. Having lived with Sheldon for seven years, he and Leonard are best friends. However, mild-mannered Leonard can become very agitated by many of his eccentricities and often feels obligated to explain Sheldon's behavior and serve as a mediator between him and other people in many situations - he has been described as the straight man of the series. While Leonard, along with his geek friends and fellow scientists, is somewhat socially inept, Leonard would like to be better accepted outside of his social group. Leonard is more well-adjusted than his companions, being more willing to try different things. The writers have toyed with a romance between him and neighbor Penny, with their unresolved sexual tension being a major force for drama.

Career
Dr. Leonard Hofstadter is an experimental physicist at the California Institute of Technology and has been published in peer-reviewed journals. In the past, he conducted classified government research on military rocket fuel capable of generating over 8,000 kN of thrust when mixed into Tovex in order to create a combustible gel. His work often includes the use of lasers, and his research topics have varied from Bose-Einstein condensates and fundamental tests of quantum mechanics to cosmic radiation and dark matter. According to Sheldon, most of his work is extremely derivative.

With Sheldon, 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. The findings contained therein show that at temperatures approaching absolute zero, the solid becomes a super-solid, a previously unknown state of matter, and the moment of inertia changes.

To study the soft component of cosmic radiation at sea-level, Leonard designed an experiment using a helium-neon laser. When the university received a new free-electron laser, he required access in order to perform his X-ray diffraction experiment.

His investigations into dark matter were rendered useless by Dr. David Underhill's observation of high-energy positrons, the first conclusive evidence for the existence of galactic dark matter. Yet, together, they examined the radiation levels of photomultiplier tubes for a new dark matter detector. He later attempted to replicate the dark matter signal found in sodium iodide crystals by the Italians.

As Sheldon's string theory-motivated search for magnetic monopole signals was unsuccessful, Leonard has carried out a series of proton decay experiments with negative results. His latest experiment consisted of twenty thousand data runs and no statistically significant results.

Dr. Hofstadter's tests of the Aharonov-Bohm quantum interference effect reached an interesting point when examining the phase shift due to an electric potential, wherein he set up the voltages using tunnel junctions. Though, given the parameters of his experiment, the transport of electrons through the aperture of the nano-fabricated metal rings was qualitatively no different than an experiment already conducted in the Netherlands. Their observed phase shift in the diffusing electrons inside the metal ring already conclusively demonstrated the electric analogue of the Aharonov-Bohm quantum interference effect.

Characterization
Although Leonard feels at home with his geek colleagues, he is reluctant to let others know about his recreational activities (such as Klingon Boggle), as he does not like to be seen as a geek, and wants to be more social. Sweet but sarcastic, Leonard also seems to be the most well-adjusted one of the group; he is quick to try new things apart from his nerd friends. Among the main characters, he generally has the least amount of difficulty interacting with "ordinary" individuals, as compared to Sheldon (who is unable to grasp social norms), Raj (who is unable to talk to women unless under the influence of alcohol), and even Howard (who is often seen as "creepy" when flirting with women). Between Sheldon and him, Leonard is the only one who feels that he "should do something" when Penny begins to recount her recent breakup. Though, Leonard also has the ability to blurt out the wrong things in front of women when he is shy, such as when he's trying to invite Penny to lunch and mentions that curry is a natural laxative.

Despite his attempts to reject his nerd status, Leonard owns, among other things, Star Wars hygiene products, an expansive Superman comic book collection and a Battlestar Galactica Colonial warrior's flight suit. Early in the series, Leonard tried to get rid of his collectables to show maturity and impress Penny. However, he changed his mind when he saw Penny was already dating another man.

Leonard is indicated to be proficient in literature, history, and music as well as the sciences - he is able to solve a woman's crossword puzzle in a matter of seconds, the answers being mostly literature-based, and can play the cello.

Having lived with Sheldon for seven years, he and Leonard are best friends, and is obligated to explain Sheldon's behavior and serve as a mediator between him and other people in many situations. However, Leonard can get very irritated by much of his behavior. For instance, when Penny and Sheldon engaged in fierce dispute, Leonard gave Penny the phone number of Sheldon's mother so she would call her son and scold Sheldon for his behavior, thus ending the fight, as shown in the episode The Panty Piñata Polarization. Leonard is also upset for the fact that Sheldon dislikes his favorite show, Babylon 5. He dislikes his friends' habit of rattling off different trivial facts, something to which all the other geniuses enjoy both listening and participating. Leonard's IQ of 173 is not as high as Sheldon's and the latter has scoffed at Leonard's whiteboard theories as common enough to be "scribbled on the wall of every men's room at MIT". Leonard seems to get along with Howard, and was obligated to ask Howard for help when he wants to get a girlfriend, as seen in one episode. Even so, Howard tried to even make Leonard's birthday a surprise, even going as far to going to the hospital, with Leonard admitting that Howard cares for Leonard. Leonard and Raj do seem to go along well, but Leonard is quite irritated by much of his impulsive and eccentric behavior, especially when it comes to explaining about the United States.

Rather short for a man, Leonard is lactose intolerant, asthmatic, bespectacled due to myopia, prone to carsickness and migraines, suffers from sleep apnea and possesses a genetic predisposition to heart disease. Leonard's primary health concern is his lactose intolerance; he avoids eating even small amounts of dairy products (including cheese, yoghurt, and butter), in addition to melon and desserts at the Cheesecake Factory, for fear of his intestines blowing up like a balloon animal and passing a noxious gas that Sheldon maintains can be weaponized. According to the pilot, he cannot process corn either. He is self-conscious about his childhood bed-wetting, particularly given his middle name is Leakey (similarly, he despises that "nerd" is in his first name). Leonard is somewhat neurotic, unsurely tilting his head as he speaks nervously as well as avoiding eye contact, and when under great stress, his voice is protracted to a high-pitched whine or he gets sweaty. Clumsy, he often bangs his head, which induces vomiting. Leonard is usually seen wearing his characteristic black-framed glasses, neutral-colored jackets over a hoodie, low-cut black Converse All Stars sneakers, brown trousers, and physics-themed t-shirts. Along with questionable fashion choices including mismatched color schemes, he sometimes applies an absurd amount of hair gel. However, his girlfriends buy him new clothes, and he has put aside his corduroy suit for formal occasions to don a fancy silk shirt and vest or blazer, much to Penny's approval.

Family
All of the members of Leonard's family are accomplished scientists, apart from his younger brother. Leonard is actually the least successful of his family. His mother, Dr. Beverly Hofstadter, is a psychiatrist and neuroscientist who has a personality identical to Sheldon's, including strict speech patterns, lack of social conventions, and attention to detail, and is mainly responsible for the difficult childhood Leonard had. Due to his mother's views, Leonard never celebrated his birthday when he was a child, and when she visited him, she didn't see the point of seeing Leonard's unoriginal research, since it has already been done. Leonard mentioned to Penny that when he was young he built a "hugging machine," with two self-constructed remote-controlled arms, in order to compensate for the lack of affection from his mother; the saddest thing was that his father used to borrow it too. Beverly also mentioned to Howard that Leonard's brother and sister are more successful in their respective fields than he is, but she wasn't proud of them as they weren't her accomplishments. Leonard's younger brother, Michael, is a Harvard law professor and is married to the youngest appellate court judge in New Jersey history, and Leonard's sister is a cutting-edge medical researcher working with adolescent gibbons to cure diabetes, by growing a human pancreas in them. Leonard also says that she is 38 years old and married. Leonard also says that his brother is eight inches taller than him.

Leonard's father is briefly mentioned as an anthropologist. Sheldon pointed out that Leonard's middle name, "Leakey", comes from famed archaeologist Louis Leakey, with whom Leonard's father had worked.

Leonard's Uncle Floyd was briefly mentioned in The Maternal Capacitance as the only person from his childhood he had fond memories about. In The Codpiece Topology, though, he said Aunt Edna, a very hairy woman, is sweet and would tickle him when they hugged. The closest thing he ever had to a birthday party was when his grandfather died on his birthday, so he got to see his cousins and have his favorite, German chocolate cake.

There is male pattern baldness in his family. According to Sheldon, when his uncles sit around the dinner table they look like a half carton of eggs.

Relationships
Leonard is usually mildly shy around women but, unlike Sheldon, he actually cares about having a girlfriend.

Joyce Kim
Joyce Kim was one of Leonard's relationship that was widely talked about in his social circle but was never seen until a flashback in 'The Staircase Implementation'. A North Korean spy attempting to get information on the government project Leonard was working on (a type of Rocket Fuel), the relationship lasted only 27 days before Joyce defected back to North Korea.

Penny
He is instantly captivated by the presence of Penny during the Pilot episode, and from that moment Leonard sets his mission to date her. He falls head over heels for Penny within seconds of spotting her and, while at first it seems like lust rather than love, by the end of the Pilot episode he has already announced to Sheldon "our babies will be smart and beautiful." Sheldon, however, is quick to add, "not to mention imaginary." His infatuation with Penny becomes the major force that drives the series during the first season. At the season one finale, Leonard finally managed to ask Penny out, and they had their first date. Subsequently, they broke up because Penny felt she wasn't as smart as Leonard would like. In another occasion, during the visit of Leonard's mother, Leonard and Penny came very close to having sex, but he ruined the moment by talking about their childhood issues with his mother and her father, respectively.

In the second season finale, when the guys were going on a 3-month scientific expedition, Penny finally showed interest in Leonard, but kept her feelings a secret. In the third season premiere, Leonard and Penny finally started a romantic relationship, and made love for the first time. They remain to have a stable relationship and even had the blessing from his mother during her second appearance during episode, The Maternal Congruence. The relationship eventually came to an end during The Wheaton Recurrence after Penny was not able to tell Leonard that she loved him as well. They decided during The Spaghetti Catalyst that they able to stay as friends as well even though they broke up (for Sheldon's sake). Penny's father would later beg Leonard to "not give up on her".

In "The Isolation Permutation", Sheldon became angry when he had to spend the night consoling a hearbroken Amy from being left out of the bridesmaid dress shopping by Penny and Bernadette. He told Howard and Leonard to keep their women in line. Leonard responded that he should not be the person to do that since he was no longer her boyfriend. Sheldon told that since Leonard was the person who invited Penny to lunch the first time she moved to the apartment, everything about her is on Leonard.

In "The Ornitophobia Diffusion", Leonard agreed to go out with Penny to a movie just as friends, their first attempt at going out alone together since they broke up. The first-half of the non-date went well, with the two finally watched a movie that Leonard picked, a documentary about building a dam on a river in South America, and Penny actually had to pay for her own ticket. The reason being that Leonard no longer gave in to Penny since he was no longer expecting sex at the end of the night. The two later went to Brady's Beer and while Leonard went to get them fries (which Penny had to pay for hers since Leonard did not want her to eat his fries), Penny started flirting with a geeky screenwriter named Kevin. A ditched Leonard started flirting with a woman named Laura, before Penny suddenly interfered. The two ended up saying horrible things to each other, such as Leonard owned two Star Trek costumes that he wore even when it was not Halloween and Penny thought that Cold Wars were fought only during the winter. They ended the night walking back to the apartment, both looking gloomy. Leonard told that he did not think they were ready to go out as friends and apologized for his behavior. Penny apologized too but said that she liked the take-charge and cocky Leonard. She said goodnight and went to her apartment.

Elizabeth Plimpton
Dr. Elizabeth Plimpton is a colleague of Sheldon who stays with Leonard and Sheldon when she visits CalTech for a conference. The first night she seduces Leonard before attempting to set up a gang-bang with Leonard, Howard, and Raj. Raj gets rid of the other two, and Leonard did not pursue a relationship past the one-night stand.

Leslie Winkle
Leslie Winkle is a fellow scientist of Leonard. The first time Leonard asked Leslie out he was rejected. His further relationships with her proved to be only short-lived casual sexual intercourse. Prior to his later encounters with Wil Wheaton, Sheldon considered Leslie his archenemy and one of their disputes resulted in the final breakup between Leslie and Leonard after Leonard supported Sheldon's theories over her own.

Interestingly, Leonard's and Leslie's actors also had a relationship in the older sitcom, Roseanne

Stephanie Barnett

 * Main Article: Leonard and Stephanie

Leonard was indirectly introduced to Dr. Stephanie Barnett by Howard who was interested in her. Leonard then stole her from Howard and started a stable relationship with her. Although the relationship went well, even earning Sheldon's approval, Leonard felt uncomfortable with Stephanie moving in with him, and they broke up, the details of their breakup—why and when—unknown.

Priya Koothrappali
Priya is Raj's younger sister, she was first introduced to the gang on April 12, 2005, on that day Leonard was able to establish a sexual relationship with her despite his pact to not do so with Howard. Their relationship was not known by the gang for five years, where Leonard continued his sexual relationship with Priya. By this point, Leonard wanted to proceed with their relationship, even suggesting to move to India with her, but Priya had no interest in proceeding

In The Cohabitation Formulation, Priya and Leonard discussed their relationship and decided to start dating each other, much to Raj's dismay. In The Roommate Transmogrification, it was revealed that Priya was moving back to India. In spite of the physical distance between them, Priya and Leonard are at present attempting to maintain a long distance relationship, communicating via Skype.

Leonard and Priya's relationship seems to have come to an end after Leonard admitted to making out with a comic book artist and admitting it to Priya and apologising, Priya then admitted she slept with her ex-boyfriend. Leonard then closed the laptop and he claimed he was single in The Isolation Permutation after leaving Sheldon at Amy's apartment.

Alice
Alice is a girl who meets Leonard at the comic book store and then seduces him. This occurs during the period when Leonard is having a long distance relationship with Priya. Leonard initially gives in to temptation, but at the last minute pulls away. Next time he's communicating, via the webcam, with Priya, he confesses his weakness. To his surprise, Priya has no problems with it. Upon questioning, Priya reveals that she has not been faithful to Leonard.

Trivia

 * Leonard wants to achieve a Nobel Prize someday (though Sheldon doubts he'll ever achieve it).
 * Leonard, as a physicist, is skeptical of loop quantum gravity.
 * Whilst Leonard's IQ is never stated in a show, he states in the Pilot that Leonard and Sheldon have a combined IQ of 360. Sheldon states that his IQ is 187, so therefore Leonard must have an IQ of 173. However, Sheldon also states his intellect cannot be accurately measured by a "regular" IQ test.
 * Leonard received his PhD at age 24
 * Leonard has a grandmother with Alzheimer's that came to Thanksgiving and stripped naked, carving the turkey.
 * Leonard wears boxer shorts.
 * Leonard always wears neutral colored sweat jackets.
 * Leonard wears black framed glasses (he originally wore tortoise shell glasses eight years ago), even if in costume.
 * Leonard cannot process corn and is lactose intolerant (if he does eat dairy products, he will fart).
 * Despite his lactose-intolerance, however, Leonard can actually process small amounts of non-fat ice-cream without farting (according to Sheldon).
 * Leonard has Darth Vader 'No More Tears' shampoo and Luke Skywalker Hair conditioner.
 * Leonard is a huge Superman fan, so much so that he owns all of the Superman films and more than 2600 Superman comics, as well as Superman underwear. He also has an unseen Superman costume with new boots that adds three inches to his height, which wore at the comic book store's annual New Years eve party when the group went as the Justice League. However, Sheldon says he is their weak point, and he got replaced by Penny's friend Zack at the most recent party.
 * Leonard is commonly seen wearing "Geek Wear" (clothes that are scientifically inspired) such as, in episode 1x03 where he can be seen wearing a shirt with a "Paradox" molecule.
 * Leonard and Sheldon own Dell XPS computers. but after The Bozeman Reaction he owned a Dell Adamo XPS
 * Leonard can play the cello mirroring Johnny Galecki's, the actor who plays Leonard, own talents.
 * Leonard's middle name is Leakey (named for the famous anthropologist that his father worked with. "it had nothing to do with your bedwetting").
 * Leonard and all his friends play Halo 3 every Wednesday.
 * Leonard and Sheldon are named after actor and producer Sheldon Leonard.
 * Leonard has an iPhone.
 * Leonard's parents are presumably not comfortable with his choice of vocation or limited earning potential, as Raj's father puts it.
 * Leonard is unaccustomed to observing birthdays, by choice of his mother's views on psychiatry.
 * Leonard's parents live in New Jersey.
 * Leonard drove a silver Volvo with a luggage rack on top early on in the show.
 * Leonard, if dumped, will go on a two week cycle of emo songs and calling Sheldon down to pet stores to look at cats.
 * Leonard owns a large collection of toys, games and memorabilia which Howard nicknamed "Nerdvana".
 * Leonard plays lead guitar on Rock Band.
 * Leonard plays Age of Conan with the guys and is probably an Assassin (his character can be seen when he is checking on Penny via the game).
 * Leonard has sleep apnea.
 * Leonard gets carsick unless he sits in the front, and "even then it's iffy".
 * Leonard has trouble making eye contact, only being able to do so with Penny and the rest of his friends, which could be indicative of Asperger's, ADD, or simply social anxiety.
 * Leonard is the group's (not including Penny) Wii bowling's 'Team Captain'.
 * Leonard's last name (Hofstadter) is in honor of Nobel Prize Winning Physicist Robert Hofstadter, who worked at Stanford University in the field of Nuclear Physics.
 * Leonard owns a green-colored Star Wars Lightsaber as seen in The Big Bran Hypothesis.
 * Leonard has a terrible habit of picking his nails or playing with his hands when he engages someone in conversation, mostly Penny.
 * Leonard dislikes his name since it has "Nerd" in it saying he prefers the name Angelo as it has "angel" and "jello" in it, although he was hallucinating that time.
 * Sheldon says Leonard hates Greek food, but he says not as much as him. This can be seen as a double meaning: Leonard doesn't hate Greek food as much as Sheldon hates Greek food and Leonard doesn't hate Greek food as much as he hates Sheldon.
 * Leonard tried wearing contacts in 7th grade, but could never get used to them.
 * Leonard can hear Penny flushing the toilet in her apartment.
 * Leonard was his school's debate club president.
 * He has been dating Priya for 6 episodes from The Cohabitation Formulation.
 * Leonard used to be stuffed in his own cello case. He believes he would have looked cooler when his classmates did this to him if he was wearing contacts.
 * Leonard believes he is the "King of foreplay", as he used to do lengthy shows for Penny before they had sex.
 * Beverly Hofstadter and Sheldon believe Leonard has Narcissistic Personality Disorder due to his childhood issues with his mother.
 * Leonard gets asthma attacks when he has panic attacks.
 * He is only main male character who wears glasses.
 * He is the only character who has had five girlfriends Joyce Kim, Leslie Winkle, Penny, Stephanie Barnett and Priya Koothrappali ), followed by Howard with four girlfriends Christy Vanderbel, Leslie Winkle, Lisa and Bernadette Rostenkowski).
 * He is afraid of horses.
 * Despite being short, Leonard states he is "too tall to be a jockey".