List of The Big Bang Theory characters

The following is a list of characters from the American situation comedy The Big Bang Theory created and executive produced by Chuck Lorre and Bill Prady, which premiered on CBS on September 24, 2007. It concerns two prodigies in their 20s, one a theoretical physicist and the other an experimental physicist, who work at Caltech and live across the hall from a waitress with show-biz aspirations. Their geekiness and intellect are contrasted by her social skills and common sense. However, it is revealed in Season 3 that the geeks weren't always so lacking in social skills.

Main characters

 * Dr. Leonard Hofstadter (Johnny Galecki) is an experimental physicist with an IQ of 173 who received his Ph.D. when he was 24 years old. He shares an apartment with colleague and friend Sheldon Cooper. Leonard is the straight man of the series. The writers have toyed with a romance between him and neighbor Penny, with their unresolved sexual tension being a major force for drama. Leonard dated Penny for most of Season 3, and while they have since broken up, some sexual tension is still apparent. Previous to Penny, Leonard had romantic relationships with co-worker Leslie Winkle, and Stephanie Barnett. Leonard's family is composed of many accomplished scientists including his mother, Beverly Hofstadter, and his brother and sister. Leonard wears glasses and has lactose intolerance.
 * Dr. Sheldon Cooper (Jim Parsons) is a theoretical physicist, possessing a master's degree, two Ph.D.s, and an IQ of 187. Originally from East Texas, he was a child prodigy, starting college at the age of 11, and receiving his first Ph.D at age 16. He is calculating and cynical, and is asexual. Sheldon exhibits a strict adherence to routine, a lack of understanding of irony, sarcasm and humor, and a complete lack of humility; these characteristics are the main sources of his character's humor and the center of a number of episodes. Sheldon's family is very different from him; his mother, Mary, is a devoted Christian, and his twin sister, Missy, is not a scientist by any means. Sheldon is consistently the geekiest character in the show.
 * Penny (Kaley Cuoco), (the only main character whose last name is not revealed) is Leonard and Sheldon's neighbor across the hallway. Originally from Omaha, Nebraska, she is a waitress at the local Cheesecake Factory and also an aspiring actress. Penny is very outgoing, kind, and assertive, her personality contrasting with those of the guys. She has dated several men during the course of the series, including former boyfriend Kurt, and Stuart (from the comic book store). Penny toyed with the possibility of dating Leonard more than once throughout the show. They dated for most of season 3 but have since broken up. In the most recent episodes, she has shown to be influenced by her geek friends, including an obsession with on-line gaming and making references to Star Trek, to her own surprise. For the most part she cannot stand Sheldon's nerdy, crazy personality, but at times they have shown to be good friends.
 * Howard Wolowitz (Simon Helberg) is a Jewish engineer at Caltech's Department of Applied Physics who often hangs out at Leonard and Sheldon's apartment. Unlike Sheldon, Leonard, and Raj, Howard lacks a doctorate. He defends this by pointing out that he has a master's degree in Engineering from Massachusetts Institute of Technology. Howard fancies himself a ladies' man and provides outrageous pick-up lines whenever a female is present. He still lives with his mother, who is overly oblivious to his accomplishments as an engineer. Howard is allergic to peanuts, and they are a serious threat to his life.
 * Dr. Rajesh "Raj" Koothrappali (Kunal Nayyar) is Howard Wolowitz's best friend, and yet another genius of the group; his name is usually shortened to "Raj". He is originally from New Delhi, India, and he works in the Physics department at Caltech, where his area of expertise is particle astrophysics. Raj is extremely shy when it comes to dealing with women; he is unable to speak to them unless he drinks alcohol. When Penny is around, Raj usually whispers what he wants to say to Howard or Leonard, who then responds out loud. Despite his pathology, Raj has often ended up in bed with women, leaving the other guys perplexed. Raj communicates with his parents, V.M. Koothrappali and Mrs. Koothrappali, in India through a webcam.
 * Dr. Leslie Winkle (Sara Gilbert) (main cast season 2, recurring seasons 1,3) is another physicist who works in the same lab as Leonard. In appearance she is essentially Leonard's female counterpart, equipped with the black framed glasses and sweat jackets. She does not get on well with Sheldon and frequently mocks him, calling him "dumbass". Leslie is known for being promiscuous, and she had casual sex relationships with Leonard first, and then Howard.

Recurrent characters
These characters appear in several episodes. The list is sorted by chronological order of appearance, considering their first appearance in the show.


 * Kurt (Brian Patrick Wade): A muscular intimidating bully, Kurt is Penny's ex-boyfriend at the beginning of the series. In the pilot episode Leonard and Sheldon went to his apartment and tried to retrieve Penny's TV set from him, but they did not succeed and returned home without pants. Penny left him because he cheated on her, but he was still invited to her Halloween party. When Penny experienced financial difficulties, Leonard and the guys tried to convince Kurt to pay Penny back money he owed her; at first Kurt refused, but eventually he paid Penny back to date her again.
 * Dr. Eric Gablehauser (Mark Harelik): The head of the Physics Department, Dr. Gablehauser is the guys' boss at the university. In his first appearance, he fired Sheldon after Sheldon insulted his intelligence. Eventually, Sheldon was rehired because Gablehauser became infatuated with Mary Cooper, Sheldon's mother. Dr. Gablehauser was also responsible for introducing Dennis Kim to the university and for hosting the Physics Bowl.
 * Mary Cooper (Laurie Metcalf): A devout Christian from Texas, Mary is Sheldon's mother. She has two other children besides Sheldon, including Sheldon's fraternal twin sister, Missy. Mary herself is not intellectual but is very wise; she appears to be an extremely good mother and is the only one who has ever been able to control Sheldon. Leonard described Mary as Sheldon's "Kryptonite". When Penny and Sheldon engaged in a fierce dispute, Penny called for Mary's help, who subsequently called and scolded Sheldon about his actions.
 * Dr. V.M. Koothrappali (Brian George) and Mrs. Koothrappali (Alice Amter): Raj's parents in India, they communicate with their son via video chat and constantly try to arrange dates for him. They want their son to marry a woman of Indian descent, and give them grandchildren. Mrs. Koothrappali is especially worried that, despite Raj being old enough to marry, the closest they have to a daughter-in-law is the "Jewish friend", Howard. Although in many episodes Raj mentions that he grew up in poverty, his friends remind him of the contrary by pointing out that Dr. Koothrappali is a gynaecologist and drives a Bentley. The Koothrappalis enjoy Doogie Howser reruns, which are apparently new to India.
 * Mrs. Wolowitz (Carol Ann Susi): Howard's overbearing Jewish mother, she is never seen on-screen but her voice is heard when he is at their house or when he talks to her on the phone. She talks to Howard always by yelling at him from another room, which results in awkward conversations with Howard yelling back at her. Mrs. Wolowitz seems to be oblivious about Howard's work as an engineer, and talks to him like he is still a child. She makes Howard's life miserable at home which prompts him to call her a "crazy old lady".
 * Dr. Stephanie Barnett (Sara Rue): A doctor and highly distinguished surgical resident at Fremont Memorial, Stephanie is first seen as Howard's date, but later becomes Leonard's girlfriend. When Howard's plan to let her drive the Mars rover failed, she left with Leonard and the two immediately became attracted to each other. Sheldon began meddling in Stephanie and Leonard's new relationship in an effort consolidate it, since in his eyes, Stephanie was the only "tolerable" mate Leonard had had. After several weeks of dating, Stephanie officially began living with Leonard in his and Sheldon's apartment. However, after much hesitance, Leonard told her to move out because he was uncomfortable with the pace of the relationship. Although they weren't seen breaking up on camera, evidence suggests their relationship ended. Series co-creator Bill Prady confirmed this in an interview, stating: "Stephanie was a chance for Leonard to learn that just because someone loves you, doesn't mean you'll love them back". Stephanie did her medical internship at Lawrence Memorial in Galveston, Texas, which is where Sheldon was born.
 * Barry Kripke (John Ross Bowie): An unlikable co-worker of Leonard and Sheldon's, who works in plasma physics, Kripke has a case of rhotacism where he pronounces the letters "R" and "L" as "W" in much the same way as Elmer Fudd from Looney Tunes. In his first appearance, he pitted his robot, the Kripke Krippler (or, as he says it, the "Kwipke Kwippwuh"), against the guys' robot, M.O.N.T.E., in an unofficial robot fight. On another episode, Sheldon attempted to befriend Kripke in order to gain access to an open science grid computer to carry out research, but it turned out to be futile. Kripke continued his antagonism towards Sheldon, when he pulled a prank on Sheldon when the latter was talking on a national radio show.
 * Dr. Beverly Hofstadter (Christine Baranski): Leonard's overly analytical mother, Beverly is a neuroscientist as well as a psychiatrist. Between her neurotically strict speech patterns, lack of social conventions, and attention to detail, she is Sheldon's female equivalent. The two of them share an odd non-romantic attraction to each other, which culminates in her kissing him after becoming drunk. She diagnosed Raj with selective mutism and considered Raj and Howard's relationship to be an "ersatz homosexual marriage". Beverly mentioned that Leonard's brother and sister are more successful in their respective fields than he is. Christine Baranski was nominated for an Emmy Award for for Outstanding Guest Actress in a Comedy Series for this role in 2009 and 2010.
 * Stuart (Kevin Sussman): Stuart runs the comic book store which the guys frequently go to. He is also a nerd, but he has a talent for drawing, is a graduate of Rhode Island School of Design and possesses a few more social skills than they do. During Stuart's first appearance, the guys brought Penny along to the store and he managed to ask her on a date. The date went fine until Stuart was dragged into discussing comic books by Sheldon. On a second date with Penny, Stuart asked for Leonard's advice, but feeling threatened, Leonard ultimately gave him bad advice. The date went fine, but when Penny was with Stuart she mistakenly called him "Leonard", leaving him devastated. Stuart was the partner of Wil Wheaton in the card game tournament, where they defeated the pair formed by Raj and Sheldon. As Stuart runs a comic book store, he has an almost encyclopedic knowledge of comic books.
 * Bernadette (Melissa Rauch): A waitress paying her way through graduate school microbiology studies, Bernadette is introduced to Howard by Penny. At first she and Howard do not get along, as they appear to have nothing in common. They find out they both have overbearing mothers they feel a connection. Subsequently, Howard realizes Bernadette is a real opportunity to develop a lasting relationship, and in an impulsive manner he proposed to her. Although Bernadette rejects his offer, they remain a couple for a time, due to Wolowitz singing a heartfelt song for her at the Cheesecake Factory, which Penny finds quite embarrassing but Bernadette finds romantic. Eventually they break up.
 * Althea (Vernee Watson) A character that made an appearance in the pilot episode, The Peanut Reaction episode, and in the opening episode of the fourth season.

Minor characters
These characters appear in fewer episodes, some in just one. The list is sorted by chronological order of appearance, considering their first appearance in the show.


 * Joyce Kim (Ally Maki): A previously unseen character who appears in The Staircase Implementation, Joyce Kim used to be mentioned as a former girlfriend of Leonard whose relationship with her only lasted a month, after which she defected back to North Korea. However, in The Staircase Implementation, Leonard admits that she wasn't a girlfriend, but a North Korean spy who attempted to get secrets from him by seducing him.
 * Christy (Brooke D'Orsay): A friend of Penny from Nebraska, Christy suddenly decided to move in with Penny. Being promiscuous, Christy ends up sleeping with Howard, who in turn invites her to move in with him (and his mother). Mrs. Wolowitz and Christy end up having a fight, and the latter leaves.
 * Toby Loobenfeld (DJ Qualls): A research assistant with a double major in Physics and Theater, Toby was used by Sheldon to play his fictional first cousin "Leopold Houston", a character Sheldon invents as part of an elaborate lie told to avoid going to see Penny sing. Cousin "Leo" is a recovering drug addict who ends up cuddling with Penny on the couch, much to the chagrin of Leonard.
 * Dennis Kim (Austin Lee): Dennis is a 15 year old genius from North Korea whom Dr. Gablehauser hopes to recruit into their Ph.D. program. Dennis and Sheldon have an antagonistic relationship when the former excels Sheldon in every way. The guys make arrangements so Dennis can meet girls of his age and get distracted of his own research. The plan succeeds and Dennis is seen kissing with a girl, no longer an intellectual threat to Sheldon.
 * Missy Cooper (Courtney Henggeler): Missy is Sheldon's fraternal twin sister who is intellectually much unlike him. Tall and attractive, she immediately catches the attention of Leonard, Howard, and Raj. Sheldon realizes that within Missy's eggs lies the potential for another "superior mutation" like him. He temporarily erects himself as a guardian to Missy in order to choose the best mate for her. Missy refers to Sheldon as "Shelly", and despite their differences she loves him and is proud of his accomplishments.
 * Lalita Gupta (Sarayu Rao): A childhood acquaintance of Raj, she is now a dental student at USC. Raj's parents set up a date for their son with her. During the date, Raj can only speak to her after drinking an alcoholic beverage (a "grasshopper"). Sheldon insists she bears a remarkable resemblance to Princess Panchali, an Indian princess in a children's story. Eventually, Lalita leaves the obnoxious and drunk Raj to have dinner with Sheldon.
 * Ramona Nowitzki (Riki Lindhome): A graduate student, Ramona is a huge fan of Sheldon's. After a lecture, she arranges to have dinner with him in his apartment. The next few days she becomes a permanent presence in his life, pressuring him to concentrate on his research and avoid distractions. Sheldon gets tired of her but is unable to dissolve their "relationship". Eventually, Sheldon reaches a breakthrough in his work, and kicks Ramona out when he refuses to share credit with her for the discovery.
 * "Captain Sweatpants" (Ian Scott Randolph) and "Lonely Larry" (Owen Thayer): Nerds that are seen at the comic book store. Captain Sweatpants is a middle-aged bald man who wears grey sweatpants and a City of Heroes T-shirt. Lonely Larry wears a brown suit and is extremely thin.
 * Dr. David Underhill (Michael Trucco): A MacArthur Genius Grant recipient, David is an experimental physicist like Leonard, who is excited to be working with him. With his leather jacket and handsome looks, Penny is shocked to know that David is a scientist and starts dating him. They break up when she finds out he is married.
 * Alicia (Valerie Azlynn): Alicia is a young blonde who moves into the apartment right above Leonard and Sheldon's. Penny displays a fit of jealousy at this turn of events, thinking that Alicia is supplanting her in the boys' attention. Alicia is an actress, although more successful than Penny, having landed a role on CSI as a (dead) prostitute. Eventually, to Howard's delight, she and Penny get into a catfight.
 * Dr. Crawley (Lewis Black): An entomologist at the University, Dr. Crawley is visited by Sheldon, Howard, and Raj in order to identify the species of a cricket they found. He is agitated at losing his position at the university, his lab, and, as a result of an extended research trip, his wife.
 * Bethany (Molly Morgan), Sarah (Sarah Buehler), and Skeeter (Andy Mackenzie): Characters that appear in The Gothowitz Deviation episode. Bethany and Sarah are a couple of girls that Wolowitz and Raj meet in a Goth club. They then go to a tattoo parlor, where Skeeter is the tattoo artist. The name Skeeter is not used on the show, only in the credits.
 * Abby (Danica McKellar) and Martha (Jen Drohan): With Leonard and Howard busy on a double date with Penny and Bernadette, Raj and Sheldon attend a university mixer where they meet Abby and Martha. Abby takes a liking to Raj, while Martha tries to connect with Sheldon. While Raj and Abby end up kissing, Sheldon completely ignores Martha, who even tries to go to bed with him.
 * Sandy (Yeardley Smith): A bureaucrat who interviewed Sheldon for a menial job in The Einstein Approximation episode. The name "Sandy" was not used on the show, but appeared in the credits.
 * Officer Hackett (Julio Oscar Mechoso), a police officer who comes to investigate the burglary in Sheldon and Leonard's apartment in "The Bozeman Reaction episode. His name is not mentioned in the episode itself, only in the credits.
 * Glen (Kevin Brief): A security guard who has a minor speaking role in The Einstein Approximation episode. The name "Glen" was not used on the show, but appeared in the credits.
 * Venkatesh Koothrappali (Frank Maharajh): Raj's cousin, a lawyer in India, who tries to negotiate a deal for Raj's part of the Ring from LOTR. He, by his own admission, is a bad negotiator, and doesn't get Raj even one of the two JetSkis he wanted.
 * Dr. Elizabeth Plimpton (Judy Greer): A renowned cosmological physicist from Princeton University known for her work in quantum cosmology who comes as a personal guest of Sheldon in The Plimpton Stimulation episode, and winds up having sex with Leonard and Raj, and expresses a desire for a foursome with Leonard, Raj, and Wolowitz.
 * Amy Farrah Fowler (Mayim Bialik): A woman Raj and Howard meet on an online dating site using a faux account for Sheldon. She organises a date with Sheldon, as she has a long-standing arrangement with her mother that she will date once a year, which Howard and Raj blackmail Sheldon into attending. Sheldon at first is sceptical, but after sharing a conversation with her, in which she exhibits characteristics and opinions similar to Sheldon, and then flat refuses to touch or have sex with him, Sheldon immediately offers to buy her a drink after a short pause, horrifying Raj and Howard. Amy is essentially a female duplicate of Sheldon.
 * Zack (Brian Thomas Smith): A man whom Penny dates after her break-up from Leonard. Leonard invites Penny and him up on the roof to watch their experiment bouncing laser beams off the moon. He has no clue what is happening. Later, he and Penny go out on a date; she is so put off at how stupid he is that she runs back to Leonard to have sex, saying that Leonard has ruined her for stupid guys.
 * Mrs. Gunderson (Lauri Johnson): Third floor neighbor of Leonard and Sheldon who hears Leonard and Penny having sex and feels compelled to comment on it.
 * Sebastian (Steven Yeum) Sheldon's former apartment-mate who left Sheldon under bad terms. Leonard replaced Sebastian as Sheldon's apartment-mate. Sebastian makes a single appearance in The Staircase Implementation where his character name is not used in the episode, but listed in the credits.
 * Louie (Ajgie Kirkland) A former occupant of the apartment in which Penny lives. He is a cross dresser whom Leonard mistakenly runs into in The Staircase Approximation episode. The name Louie is used by Sheldon, referring to him/her as Louie/Louise.

Notable guest stars appearing as themselves

 * Ira Flatow (Season 3, The Vengeance Formulation): Sheldon is invited to talk about magnetic monopoles on Flatow's radio show, Science Friday. However, Barry Kripke pulls a prank on Sheldon, and Sheldon is publicly humiliated to a nationwide audience.
 * Summer Glau (Season 2, The Terminator Decoupling): When the guys travel by train to a conference in San Francisco, they realize Summer Glau (a Terminator in Terminator: The Sarah Connor Chronicles) is sitting in the same passenger car. Raj, Howard, and Leonard take turns talking with her. Raj can't talk without drinking beer (which turned out to be non-alcoholic), Howard is his usual creepy, over-the-top self, and Leonard can't start a conversation before she has to get off the train.
 * Stan Lee (Season 3, The Excelsior Acquisition): When Sheldon has to miss Lee's appearance at the comic book store because he ends up in traffic court after speeding, Penny tries to make it up to him by taking him to Lee's house, uninvited and unannounced (acquiring Lee's address from Stuart). Lee is furious and sarcastically tells Penny and Sheldon to watch a basketball game with him, but Sheldon thinks Lee is serious and rushes into Lee's house. When Sheldon announces his "autographed" restraining order to Leonard, Howard, and Raj, he comments it will look great hanging next to his restraining order from Leonard Nimoy.
 * Katee Sackhoff (Season 3, The Vengeance Formulation): Howard fantasizes about taking a bath with Katee Sackhoff (Captain Kara "Starbuck" Thrace in Battlestar Galactica). However, in his own fantasy Sackhoff scolds him and tells him to get a real girlfriend instead of imaginary ones.
 * Charlie Sheen (Season 2, The Griffin Equivalency): When Raj discovers a celestial body he is very excited about it. At Penny's restaurant, Raj says to the patron at the next table over, "Hey, buddy. I'm going to be in People magazine!"; Charlie Sheen turns around and says "Yeah? Call me when you're on the cover."
 * George Smoot (Season 2, The Terminator Decoupling): After the train ride to San Francisco, Sheldon presents his paper to 2006 Nobel Prize laureate George Smoot, and proposes joint research; Smoot abruptly rejects his idea by asking "With all due respect, Dr. Cooper, are you on crack?"
 * Wil Wheaton (Season 3, The Creepy Candy Coating Corollary & The Wheaton Recurrence): In the first episode, Sheldon enters a card game tournament (Mystic Warriors of Ka'ah) to confront Wil Wheaton over an incident that occurred in 1995 when Sheldon was devastated because Wheaton (Wesley Crusher in Star Trek: The Next Generation) failed to show up at a fan convention that Sheldon attended. In the final match, Sheldon is about to defeat his hated rival, but Wheaton lies to him about the reason for missing the convention, and Sheldon throws the game out of feeling of guilt. Wil Wheaton makes a second appearance in another episode, where he breaks up Leonard and Penny's relationship in order to win a bowling competition against the main characters.
 * Steve Wozniak (Season 4, The Cruciferous Vegetable Amplification)