The Big Bang Theory - Main Cast

Main Cast

These actors have been credited in all episodes of the series:

• Johnny Galecki as Leonard Hofstadter, Ph.D. – An experimental physicist with an IQ of 173. He received his Ph.D. when he was 24 years old. He is originally from New Jersey. The straight man of the series, he shares an apartment with colleague and friend Sheldon Cooper. The writers immediately implied potential romance between him and neighbor Penny, and their sexual tension is frequently explored including occasional dating. In Season 3, Leonard begins an on-again, off-again romantic relationship with Penny, although the two continue to live separately.
• Jim Parsons as Sheldon Cooper, B.S., M.S., M.A., Ph.D., Sc.D. – Originally from Galveston, Texas, he was a child prodigy with an eidetic memory who began college at the age of 11 (after completing the fifth grade), started graduate studies at 14, and earned a Ph.D. at 16. A theoretical physicist researching quantum mechanics and string theory, he has two master's degrees, two Ph.D.s, an Sc.D., and an IQ of 187. He exhibits a strict adherence to routine and a lack of understanding of irony and sarcasm; he is also uninterested in many of the romantic hijinks of his friends. Sheldon shares an apartment with Leonard Hofstadter, across the hall from Penny, and relies on both for advice in social situations. Sheldon is very egotistical, and he often boasts about his intelligence, although he lacks social skills. Sheldon relies on his friends to drive him around, and he eventually tries to go for his driver's license but is unable to complete the task. In the fourth season, he begins a relationship with Amy Farrah Fowler, who becomes his first girlfriend during the fifth season, even though he is wary of germs and physical contact. He is a very introverted character. He is also famous for knocking on a door before saying the name of whom he's addressing, repeating this three times.
• Kaley Cuoco as Penny – From a town outside of Omaha, Nebraska, she is a blonde who lives across the hall from Sheldon and Leonard. Penny is pursuing a career in acting, and has been on casting calls and auditions but has not been very successful thus far. To pay the bills, she is a waitress and occasional bartender at The Cheesecake Factory. To date, her last name has not been revealed. She dated Leonard at the end of the first season, and during the third, fifth, and sixth seasons. By season four, Bernadette, Amy and Penny have formed their own group, who like to hang out in Penny's apartment or go out together.
• Simon Helberg as Howard Wolowitz, M.Eng. – He works as an aerospace engineer. He is Jewish, and lives with his mother. Unlike Sheldon, Leonard, and Raj, Howard lacks a Ph.D. He defends this by pointing out that he has a master's degree in engineering from MIT and that the apparatus he designs are launched into space, unlike the purely abstract work of his friends, including going to space himself in the Season 5 finale. He fancies himself a ladies' man and devises outrageous pick-up lines, with suitably unimpressed reactions from Penny and limited success with other women. He claims to be a polyglot. He dates and later marries Bernadette Rostenkowski. In the fifth season, he trained as an astronaut, and blasted off into space in the season finale to serve as a payload specialist on the International Space Station.
• Kunal Nayyar as Raj Koothrappali, Ph.D. – Originally from New Delhi, India, he works as a particle astrophysicist at Caltech. His family is very wealthy. He communicates with his parents, Dr. and Mrs. V.M. Koothrappali, via webcam. He is very shy around women and is physically unable to talk to them (except for his mother and his sister) unless he drinks alcohol, or at least thinks he has been drinking alcohol, or has taken experimental medications provided by the pharmacology department at the university. However, he has often had better luck with women than his overly-confident best friend Howard. He has very feminine tastes and often takes on a stereotypical female role in his close friendship with Howard, but he insists that he is not gay. During the fourth season, his sister Priya (Aarti Mann) stays with him and she becomes Leonard's girlfriend.

These actors were first credited as guest stars and later promoted to main cast. However, even after promotion, they are only credited in episodes in which they appear:

• Sara Gilbert as Leslie Winkle, Ph.D. (recurring season 1, starring season 2, recurring season 3) – a 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 is an enemy of Sheldon's, due to their conflicting scientific theories. Though each considers the other to be intellectually inferior, Leslie is much wittier than Sheldon, regularly calling him "dumbass", and she usually bests him in their repartee. Leslie has had casual sex with Leonard and later Howard; in the case of the former, it reunited Gilbert and Galecki on-screen after the two played the on-screen couple of Darlene Connor and David Healy during the run of Roseanne. Gilbert was promoted to a main cast member during the second season but was demoted again because producers could not generate enough content for the character. Gilbert left the series after season 3 concluded to focus her efforts on The Talk, on which she serves as executive producer for CBS.
• Melissa Rauch as Bernadette Rostenkowski-Wolowitz, Ph.D. (recurring season 3, starring since season 4) – a young woman who is initially a waitress and co-worker of Penny's, paying her way through graduate school microbiology studies, she defends her doctoral thesis and lands a high-paying science position at the end of season 4. Bernadette is introduced to Howard by Penny. At first they do not get along, apparently having nothing in common. When they find out that they both have overbearing mothers, they feel a connection. During season 3 they date and then break up off-screen, then get back together in season 4. They become engaged near the end of season 4, and marry at the end of season 5.
• Mayim Bialik as Amy Farrah Fowler, Ph.D. (guest starring season 3, starring since mid-season 4) – a woman Raj and Howard met on an online dating site after secretly setting up an account using Sheldon's name and information. The site matches her to Sheldon, and the two share many similar traits though Amy is more interested in social and romantic interaction. Once she and Sheldon meet, she becomes, as Sheldon puts it, a girl who is his friend, but not his "girlfriend". Their relationship slowly progresses through seasons 5 and 6. Amy also believes she and Penny are best friends ("besties", by her own definition), a sentiment that at first Penny respectfully indulges but doesn't share. Penny eventually becomes a real friend, overlooking Amy's Sheldon-like qualities. Amy's admiration for Penny has at times bordered on attraction. Amy Fowler has a Ph.D. in neurobiology, while Bialik herself has a doctorate in neuroscience; in the season 1 episode "The Bat Jar Conjecture", Raj suggests recruiting "The girl who plays TV's Blossom" (Bialik) to their Physics Bowl team.
• Kevin Sussman as Stuart Bloom (recurring seasons 2–5, starring since season 6) – Stuart runs the comic book store that the guys frequently visit. He is also a nerd, but he has a talent for drawing, is a graduate of Rhode Island School of Design and possesses more social skills than the rest of the guys. During Stuart's first appearance, the guys brought Penny along to the store and he managed to ask her on a date. They go on a few dates until Penny mistakenly calls him "Leonard", leaving him devastated. As Stuart runs a comic book store, he has vast knowledge of comic books and superheroes. In the Season 4 episode "The Toast Derivation", he implied he was in financial trouble and that the comic book store is now also his home. At Howard's bachelor party during the "The Stag Convergence" episode, Stuart uses his toasting turn to tell Howard how lucky he is and compares it to his own situation of living in the back of a comic book store. In Season 6, he is invited to be part of the guys' group while Howard is in space. Sheldon is not very accepting of this due to Stuart's art degree, but relents after Stuart offers him a 30% off discount in the comic book store.