The Big Bang Theory is an American sitcom created and executive produced by Chuck Lorre and Bill Prady. It premiered on CBS September 24, 2007.
Set in Pasadena, California, the show concerns two male Caltech prodigies in their twenties, one an experimental physicist (Leonard) and the other a theoretical physicist (Sheldon), who live across the hall from an attractive blonde waitress with show-biz aspirations (Penny). Leonard and Sheldon's geekiness and intellect are contrasted with Penny's social skills and common sense for comedic effect. Two equally geeky friends of theirs, Howard and Rajesh, are also main characters
The show is produced by Warner Bros. Television and Chuck Lorre Productions.In March 2009 it was reported that The Big Bang Theory had been renewed for a third and fourth season by CBS.In August 2009, the sitcom won the best comedy series TCA award and Jim Parsons won the award for individual achievement in comedy. When the third season premiered on September 21, 2009, it ranked as CBS's highest-rated show of that evening in the adults 18-49 demographic (4.6/10), along with a series-high 12.83 million viewers. The Big Bang Theory airs on Mondays at 9:30 EST following another Chuck Lorre-produced show Two and a Half Men
- Johnny Galecki as Leonard Hofstadter, Ph.D. - Leonard 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. He 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.
- Jim Parsons as Sheldon Cooper, Ph.D. - Originally from East Texas, he was a child prodigy, starting college at the age of 11, right after completing the 5th grade. As a theoretical physicist, he possesses a master's degree, two Ph.D.s, and an IQ of 187. He 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 shares an apartment with Leonard Hofstadter. According to his twin sister, Sheldon would send home his imaginary friends at the end of the day, when they were kids. Sheldon's reply: "they were not friends, they were imaginary colleagues.
- Kaley Cuoco as Penny - The attractive, blonde neighbor who lives across the hall from Sheldon and Leonard's apartment. She has aspirations of a career in show business, and has been to casting calls and auditions, but has not been successful thus far. To pay the bills, she works as a waitress for a Cheesecake Factory restaurant.
- Simon Helberg as Howard Wolowitz, M.Eng. - He works as an engineer and lives with his mother; they are Jewish. 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 the apparatus he designs is actually built and launched into space, unlike the purely abstract work of his friends. He provides outrageous pick-up lines and fancies himself a ladies man with suitably unimpressed reactions from Penny; however, he has shown some success with other women.
- Kunal Nayyar as Rajesh Koothrappali, Ph.D. - Rajesh, who originally comes from New Delhi, India, works as a Particle Astrophysicist at CalTech. He is normally very shy to the point of near-muteness in front of females; because the show's scenes often involve Penny, his paucity of dialogue has led to him occasionally being overlooked by the rest of the cast. Only alcohol and experimental pharmaceuticals have provided temporary cures to his chronic shyness. However, on one occasion he was able to squeak out an apology to Penny without the aid of either of these. His parents, introduced as Dr. and Mrs V.M Koothrappali, are seen via webcam; his father is a gynaecologist and drives a Bentley, facts that are often pointed out to him when he claims that he was raised in poverty in India
- Sara Gilbert as Leslie Winkle, Ph.D. (recurring since season 1)– She is an experimental physicist who occasionally sleeps with both Howard and Leonard during the show's airing. She does not get on well with Sheldon Cooper and frequently mocks him. She was promoted to main cast during the second season, but demoted again once the writers realized they could not produce quality material for her for every episode.