Leonard Hofstadter

Dr. 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.

Leonard is rather short for a man, and easily gets bothered by much of Sheldon's manners. He keeps a whiteboard in their living room on which he works on theoretical particle physics. While Sheldon's knowledge seems to be focused primarily in math and science, Leonard is indicated to be proficient in literature and history 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. ("Pilot") Leonard's IQ is not as high as Sheldon's; the latter scoffs at Leonard's whiteboard theories as common enough to be "scribbled on the wall of every men's room at MIT". Sheldon's IQ s 187, and says that their combined IQ is 360, meaning that Leonard's IQ is 173. Most of the equations on Leonard and Sheldon's boards feature complex higher mathematics, such as virtual particles in QM, or series of Riemann zeta functions. He is originally from New Jersey and is usually seen wearing his characteristic black framed glasses, neutral colored sweat jackets, black low top Chuck Taylor Converse, brown trousers, and physics-themed t-shirts.

Personality
Although Leonard feels at home with his geek colleagues, he wants to be more socially active. He is instantly captivated by the presence of Penny during the Pilot episode, and from that moment Leonard sets his mission to date her. In the early episodes, Leonard is reluctant to let Penny know about his recreational activities or pass time activities (such as Klingon Boggle) as he does not like to be seen as a nerd by her. He also dislikes his friends' habit of rattling off different trivial facts, something to which all the other geniuses enjoy both listening and participating. 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 and, between Sheldon and him, is the only one who feels that he "should do something" when Penny begins to recount her recent breakup. While certainly a nerd by most definitions, he is much less socially awkward than Sheldon (who is unable to grasp social norms), and even Howard (who is too "creepy") and Raj (who can't talk to women). 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. 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."

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 can also play the cello. As seen in "The Hamburger Postulate", he and Leslie practice their instruments then go to have sex after his failed attempt to woo Penny.

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. 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.

Leonard's primary health concern is his lactose intolerance; he avoids eating even small amounts of dairy products, including cheese, yoghurt and butter, for fear of passing gas. Leonard also wears glasses because of myopia, and practically cannot see without them. In "The Pancake Batter Anomaly", when Leonard's glasses were broken at the movie theater, he had to go to his apartment for his backup glasses. He was aided remotely by Howard and Raj to navigate through the living room by using a helmet camera which ended in disaster for him. At various points in the show, Sheldon also says that Leonard suffers from sleep apnea and gets carsick unless he sits in the front seat.

Hofstadter Family
All of the members of Leonard's family are accomplished scientists, apart from his younger brother. 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" 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.

Work
Leonard was 24 years old when he received his Ph.D. and currently works as an experimental physicist. His work often includes the use of lasers, such as a helium-neon laser or free electron laser, and his research topics have varied from Bose-Einstein condensates and foundations of quantum mechanics to soft cosmic rays at sea level. Leonard designs experiments in order to prove theories but, according to the cynical and egotistical theorist Sheldon, his work is mostly derivative from other scientists and thus possibly plagiarized and unimportant.

His attempts to disprove the existence of dark matter were made moot by the work of another physicist. Yet, he resolved the latter by helping to solidify proof of the hypothetical matter's existence with a photomultiplier, was invited as keynote speaker to a topical conference by the Institute of Experimental Physics for his successful research on supersolids and has showed diverse knowledge of theoretical physics.

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

Penny
Leonard became attracted to Penny within seconds of spotting her, and announced to Sheldon "our babies will be smart and beautiful". Sheldon comments "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".

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 hours before Joyce defected back to North Korea.

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.

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, athough the relationship went well, even earning Sheldon's approval, Leonard felt uncomfortable with Stephanie moving in with him, and they broke up but it is unknown why and when.

Priya
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, presumably this will end their relationship.

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 Leonards IQ is never stated in a show, Sheldon 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, though Sheldon also states his intellect can not be accurately measured by a "regular" IQ test, this may suggest that Leonard might have a higher IQ, although, this is extremely improbable.
 * Leonard received his PhD at the age of twenty four years old.
 * 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 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 them if he was wearing contacts.
 * Leonard believes he is the "King of foreplay", as he used to do lengthly shows to 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 had five girlfriends (Joyce Kim, Leslie Winkle, Penny, Stephanie Barnett and Priya Koothrapali),followed by Howard with four girlfriends (Christy Vanderbel, Leslie Winkle, Lisa and Bernadette Maryann Rostenkowski).