Total Episodes: By the time you read this, the show will likely have passed 100 episodes, as it's about halfway through the fifth season.
Original Air Dates: 2007-present
Original Network: CBS
Geek Factor: 10
Leonard Hoftstadter, Ph.D. (Johnny Galecki): An experimental physicist, often portrayed as the straight man on the series. Leonard is originally from New Jersey, and now lives in Pasadena, California, sharing an apartment with Sheldon Cooper. Both Leonard and Sheldon work at Caltech. Leonard is probably the least geeky of the main four geek characters, although he does have an expansive Superman comic book collection and a lot of other geek items! Leonard's entire family are also scientists, except for a brother who is a law professor at Harvard Law. He fell in love with Penny pretty much from the moment he first met her. They subsequently dated for a time, only to have their relationship sabotaged by Evil Wil Wheaton, but more recently got back together again, although their current relationship is in "beta testing."
Sheldon Cooper, Ph.D. (Jim Parsons): A theoretical physicist at Caltech, Sheldon is originally from East Texas. His specialty is string theory. He has no interest in romance, save from an analytical point of view. His inability to get irony, humor or sarcasm, strict adherence to routine, and other factors screams to many people that he's got Asperger syndrome. When someone accuses him of being crazy or insane, Sheldon will announce that he's not crazy, his mother had him tested. Sheldon's family is nothing like him. Sheldon doesn't care for Babylon 5, and his arch-nemesis for a long time was Wil Wheaton (who plays himself on his all-too-infrequent guest appearances).
Penny (Kaley Cuoco): Born and raised in Omaha, Nebraska, Penny (yes, she has no last name, at least that they've mentioned yet) moved to Malibu to pursue an acting career. Naturally, she works as a waitress and sometimes bartender at The Cheesecake Factory. She lives across the hall from Leonard and Shelton. Her acting career highlights have included performing in "The Diary of Anne Frank" in a theater above a bowling alley and a commercial for hemorrhoid cream.
Howard Wolomitz, M.Eng. (Simon Helberg): An aerospace engineer, and the only one of the four core group who doesn't have a Ph.D. (something Sheldon has been known to call attention to now and then). Howard lives with his very Jewish (and unseen but definitely heard) mother. When the series begins, Howard thinks of himself as a ladies' man, with all kinds of pick-up lines (none of which ever seem to work). Fortunately for Howard, Penny eventually paired him up with her fellow waitress, Bernadette Rostenkowski, and the two of them fell in love and got engaged.
Rajesh Koothrappali, Ph.D. (Kunal Nayyar): Rajesh (usually just called “Raj” or “Koothrappali”) is from New Delhi, India, and is a particle astrophysicist. His parents are very wealthy, likely due to his father being a gynecologist. Raj stays in touch with his parents via webcam (probably Skype, although I don't believe it's specifically mentioned). Raj is very shy around women, not even being able to talk to one he finds attractive unless he's had some alcohol (or thinks he has). Despite this, he had better luck with women than Howard had before Bernadette came in the picture. Raj had a major crush on Bernadette during most of the fourth season, although he seems to be over this now. His sister, Priya, is an attorney who was Leonard's girlfriend early in the current season, but they've now broken up.
Leslie Winkle, Ph.D. (Sara Gilbert): Leslie appeared on and off during the first three seasons of the show, and is basically Leonard's female counterpart, and works in the same lab that Leonard does. Because her scientific theories are opposite Sheldon's, they are enemies. Leslie got kind of involved with Leonard for a time, but it was a purely physical relationship. She later had a similar relationship with Howard. I don't believe they explained why she's no longer around.
Bernadette Rostenkowsky, Ph.D. (Melissa Rauch): Bernadette was a co-worker of Penny's at the Cheesecake Factory, working there to pay her way through graduate school microbiology. But now, she is in a high-paying science position. She and Howard initially didn't get along until they both connected over both having overbearing mothers. Interestingly, at least once, Bernadette yelled out in anger and sounded exactly like Howard's mother! Bernadette's father is apparently someone who you don't want to get angry at you!
Amy Farrah Fowler, Ph.D. (Mayim Bialik): When Raj and Howard decide to create a secret dating site profile for Sheldon, Amy is the only person who matches him. The two share many traits, although Amy seems to have more of an interest in the social niceties and relationships than Sheldon does. Amy is a neurobiologist. While Amy is a girl who is Sheldon's friend, Sheldon used to say that she is not his “girlfriend.” This, however, changed a number of episodes ago, and Shelton wrote up a "Girlfriend/Boyfriend Agreement" (similar to the infamous "Roomate Agreement" he has with Leonard) which Amy signed. She, Bernadette, and Penny have formed their own sort of core friendship group, often getting together to drink wine while one of the trio talks about their latest problem. They all hate Raj's sister. Amy has a tendency to opine that, while Bernadette is attractive, Penny is apparently Amy's idea of the most beautiful woman in the world (not that Amy seems to be oriented that way, she just has a tendency to say what she thinks).
Mrs. Wolowitz (voice of Carol Ann Susi): Stereotypical overbearing Jewish mother? Well, she's probably way beyond the worst of the stereotype presented on TV ever!
Priya Koothrappali (Aarti Mann): Raj's beautiful sister, an attorney who graduated at the top of her class. Five years before she's first seen on the show, she and Leonard hooked up in secret. When they start seeing each other again, they try to keep it hidden, but Sheldon discovers it. As of this writing, Priya moved back to India, and she and Leonard were keeping in touch via webcam. Apparently, they couldn't maintain their relationship that way and are now broken up.
Stuart (Kevin Sussman): Owner of the comic book store that the guys go to every Wednesday. A geek, but a geek with artistic ability. He actually dated Penny a few times, but when Penny accidentally called him “Leonard” the dating stopped. Stuard seems to know a lot of geek celebrities, given how much contact he's had with them. For instance, Wil Wheaton regularly buys his comics at the store; another time, Stuart manages to book Stan Lee for an appearance in the store. Stuart's store seems to be in financial trouble – odd, considering the guys probably buy all their stuff there (except for during Comic-Con, of course).
Evil Wil Wheaton (Wil Wheaton): Sheldon's arch-nemesis, ever since Sheldon took a 10-hour bus ride to attend a Star Trek convention Wil was to appear at so that Sheldon could get Wil to autograph his mint-on-card Wesley Crusher action figure. Wil didn't appear, instead appearing on The Hollywood Squares. Sheldon runs into Wil at the comic shop during the Mystic Warlords of Ka'ah card game tournament, vowing to defeat Wil, but when Wil bulls his way into convincing Sheldon that he didn't attend because his grandmother was dying, the guilt causes Sheldon to throw the game, allowing Wil to win the tournament. The next time Wil appears, he's headlining a bowling team that the guys are competing against, and he convinces Penny to break up with Leonard in order to win the game. Wil's third appearance is when he uses his celebrity status to get ahead of the guys in line for a big-screen showing of Raiders of the Lost Ark, causing the gang to not be allowed in. Sheldon then steals the print of the film and runs off with it, with Wil and a mob chasing the guys away. His last appearance to date has him inviting the guys to his house for a party (it's discovered Brent Spiner will be there). Sheldon isn't going to attend at first, but he changes his mind and shows up anyway. Wil surprises him by giving him a signed Wesley Crusher action figure, and Sheldon is so surprised that he hugs Wil. Unfortunately, Brent Spiner shows up then and, shocked to see a Wesley Crusher action figure, immediately tears the bubble off the card, causing Sheldon to make Brent his new arch-enemy.
Dr. Beverly Hofstadter (Christine Baranski): Leonard's mother, an overly analytical neuroscientist and psychiatrist. She acts a lot like Sheldon in many ways, and indeed, she seems closer to Sheldon than she is to Leonard, even telling Sheldon that she's divorcing Leonard's father long before Sheldon finds out.
Mary Cooper (Laurie Metcalf): Sheldon's mother, a devout Christian from Texas. She is Sheldon's “Kryptonite.”
Brian George, who plays Raj's father, voiced Lester Sludge and Ali Bombay on MASK, provided voices for the 1986 Dennis the Menace, voiced Botch on Camp Candy, did guest roles or voices on Darkwing Duck, The Real Ghost Busters, Quantum Leap, Batman: The Animated Series, Robin Hood: Men in Tights, The Pink Panther (1993-1995), and many other roles. He played Dr. Bashir's father in Star Trek: Deep Space Nine. He's had a very long list of geek credits besides all those. Including the voice of the Parasite and others on Justice League, Professor Warren on The Spectacular Spider-Man, and is providing the voice of Appa Ali Apsa on Green Lantern: The Animated Series.
James Hong provided a voice for two characters in the English dub of Godzilla, King of the Monsters, and appeared in a number of geek roles over the years, but might be most recognizable from his nine appearances on Kung Fu, playing different roles! He also guest starred in episodes of The Bionic Woman, The New Original Wonder Woman, and you might most recognize him as David Lo Pan in Big Trouble in Little China or as Lee Pow in The Adventures of Brisco County Jr. He's been called upon anytime they want a Chinese person who could be somewhat threatening! He appeared in two episodes as Chen, who runs the Chinese restaurant the gang prefers.
Katee Sackhoff appeared in one episode as herself, or rather, as Howard's fantasy of herself. She is, of course, best known for playing Starbuck in the re-envisioning of Battlestar Galactica. Eliza Dushku played an FBI Agent investigating Howard's background in one episode, but is probably best known as Faith on Buffy the Vampire Slayer and Angel. Keith Carradine appeared in one episode as Penny's father, and of course, his father was John Carradine, who played Dracula in House of Dracula and House of Frankenstein. Keith appeared in a few episodes of brother David's Kung Fu show, playing a counter version of Caine.
The show has had a number of other famous people appearing as themselves aside from Katee Sackhoff and Wil Wheaton. Summer Glau appeared as herself in one episode; she's known from Firefly and Terminator: The Sarah Connor Chronicles. George Takei, Mr. Sulu himself, appeared in the same episode Katee Sackhoff appeared in! Stan Lee, who needs no introduction, also appeared in an episode. Apple's Steve Wozniak is another cameoist, when Sheldon meets him and says he still has his old Apple II, Wozniak offers to autograph it, but Sheldon drops it in his haste to bring it to him. Wil Wheaton's Next Generation co-star LeVar Burton appears at the end of one episode, having been invited to a party by Sheldon via a tweet. And as of this writing, Brent Spiner is the latest geek guest-star on the show.
Geek Pedigree: Series co-creator Chuck Lorre wrote episodes of MASK, Heathcliff, Muppet Babies, Defenders of the Earth, Fraggle Rock, Beany and Cecil, and The Toxic Crusaders before writing exclusively for sitcoms (these include Roseanne and Cybill, shows in which many of The Big Bang Theory's cast members previously appeared on). Co-creator Bill Prady wrote episodes of You Can't Do That on Television, Fraggle Rock, The Jim Henson Hour, Here Come the Munsters, and Star Trek: Voyager. Director Mark Cendrowski's directed episodes of Sabrina the Teenage Witch and The Witches of Waverly Place.