These include (but are probably not limited to) the following:- Sheldon has a favorite spot on the couch in his apartment, namely the right seat on the sofa (when viewed from the front). When he finds someone sitting in his spot he will invariably state "You're in my spot!" even if he has no intention of sitting there. When seeking a place to sit in other places (e.g. a jail cell, a north pole research base, Penny's room), he will look for a similar place - usually the right side of a couch or bench in the middle of the room - claiming it as his spot with a look (and sometimes verbally).- Raj is unable to talk to women (a condition known as selective mutism) unless he drinks alcohol or thinks he is drinking. (see also FAQ above). (This is then removed at the end of Season 6) .- The elevator in Sheldon and Leonard's building is always out of order. (see FAQ above).- Howard's mother is often heard (usually yelling at Howard) but she is never seen on-screen. The only exception was a brief glimpse of her passing a doorway.- Penny comes from Nebraska, and although she acts quite civilized and somewhat sophisticated, her 'redneck' upbringing sometimes shows in her actions or interests (e.g. affinity with guns, hunting squirrels, fist fights, etc.).- Raj's parents are only ever seen on a computer screen via a Web cam or heard on the phone.- Howard is Jewish but when he is out of his house he avoids Jewish traditions as much as he can (e.g. eating non-kosher food).- Sheldon has trouble sleeping when he is sick unless someone sings the song "Soft Kitty" to him. If the song is recited incorrectly Sheldon makes the person singing start over (and over, if necessary) until they get the lyrics right, after which he will dismiss them so he can sleep.- Sheldon has frequent battles with former Star Trek actor Wil Wheaton throughout the show so much that initially Sheldon considered Wil his nemesis. Though they became friends in later seasons Sheldon continues to fight with Wil on occasion.- Sheldon has a redneck side being from Texas and occasionally alludes to it with not-so-cherished abilities such as "If you want, I'll take you outside and teach you how to shoot a raccoon so close it craps itself."- Sheldon adores his grandmother, to whom he refers as 'Meemaw'. His grandmother's nickname for him is 'Moon Pie', and only she is allowed to address him that way. If anyone else uses it Sheldon gets upset, saying "Only Meemaw calls me Moon Pie!"- While Sheldon loves just about any science fiction movie or series there is on TV, he cannot stand Babylon 5.- When Sheldon knocks on a door he always uses the same sequence: he knocks 3 times, says the person's name once, then repeats both actions twice (for a total of three sets). He did not do this the first several episodes; this particular behavior was established later in the series as one of Sheldon's quirks.- When someone brings home take-out food Sheldon will ask a list of questions concerning the food's brand, composition, additives, packaging, etc. He also has a list of condiments he prefers to use with certain take out; these items must be obtained from specific stores before he is willing or able to eat the takeout.- Penny always ignores the check-engine light on her car, and though several characters in the show have commented on this she refuses to get her car serviced.- Howard is constantly reminded by others (mainly Sheldon) that he is the only person in their group without a doctorate (he has a Masters degree in engineering from M.I.T.)- When Sheldon jokes or pulls a prank on someone he ends it with 'Bazinga!'- Sheldon has an extremely low tolerance for alcohol. Whenever he drinks it (often unwittingly) he loses all of his inhibitions, often with disastrous results.- When angered Howard often stands up in fury, but he can be coaxed back down with a little persuasion or by backing himself down.- Leonard is often reminded of a short relationship he had with a Korean girl who defected back to North Korea.- Leonard is often reminded that he has "mommy issues" because his mother refused to celebrate or acknowledge any of his personal accomplishments, thus denying him parental approval. Conversely, Penny has considerable "daddy issues"; her father really wanted a son, and tried to raise her as such.- Howard is a self-proclaimed ladies' man who tends to hit on any attractive woman within sight. Although he is aware that his awkward flirtations and lame seduction tricks never work he is persistent to the point of being masochistic, and he always finds a plus in each rejection (e.g. when Penny answers one of his attempts with, "Not with a thousand condoms" he replies, "So there IS a number?")- Sheldon required Leonard to sign an absurdly elaborate "roommate agreement" (contract) before he was allowed to move in; Leonard is constantly reminded of the ridiculous and extremely far-fetched rules and conditions in this agreement which always work in Sheldon's favor (e.g. Leonard is not allowed to whistle, and if he ever gets superpowers, he is obliged to take Sheldon as a sidekick). Sheldon also has a warning and strike system; violations of the roommate agreement count as strikes against the person who broke the rules. As Sheldon once noted, "You do not screw the roommate agreement; the roommate agreement screws you!" At one point, Ray's sister Priya, who is a lawyer, finds several loopholes within the contract that allow Leonard to get away with almost anything. However, Sheldon then blackmails Leonard into signing a new agreement (one that benefits Sheldon even more), on threat of revealing Leonard and Priya's relationship to her parents.- Sheldon has a "relationship agreement" (contract) with Amy Farrah Fowler that is purposely written so it benefits Sheldon and he regularly takes advantage of loopholes found within it to weasel out of romantic activities and anything else he deems stupid and unnecessary.- Raj often tries to win sympathy by acting as if he grew up poor, but the others (usually Howard) always counter with an example that shows his family is actually rich and privileged, which Raj immediately tries to play down (e.g. Howard mentions that Raj's father is a gynecologist who drives a Bentley (an expensive car), to which Raj replies that it is only a lease).- Even though Raj was born and raised in India he can't stand Indian food and tries to avoid it whenever and wherever possible (e.g. when the guys wonder why he doesn't want to go to the Indian restaurant they suggest, he answers in disgust "they just have Indian food...")- Sheldon's asexuality is often frustrating to Amy and she regularly tries to initiate physical contact with him, only to end up bargaining for something that works for both of them, usually something not even remotely sexual (e.g. Amy proposes to have sex with him but they end up agreeing to cuddle on the sofa). Amy also appears to be somewhat attracted to Penny and occasionally suggests they should experiment together.- Sheldon refers to sex as "coitus". He usually talks about it in the most inappropriate instances and occasionally reveals private details of his friend's (usually Leonard) sex life, which makes the women in the group (bar Amy) uncomfortable.- When Bernadette yells she sounds a lot like Howard's mother. Howard finds this attractive, remarking "she sounds sexy when she's angry!"- When a character calls Sheldon insane or crazy - which has happened several times - he always answers, "I'm not crazy; my mother had me tested!" (Sheldon's mother did say in one episode that she had him tested, but she regrets not taking him to a specialist for a "second opinion").- Stuart is poor and often borrows money. He also gives the guys a 30% discount on comics in his store in exchange for their friendship.- Stuart is usually depressed about the state of his life to the point of accepting absurd relationship statuses with various people.- Raj is the only one in the group without a significant other. Occasionally hints are dropped that Howard treated him like a pretend girlfriend, once with Howard informing him that his now wife Bernadette was now the one he was referring to as darling as opposed to Raj. In one episode Raj and Howard unwittingly make out with each other in the science lab (with the aid of separate WiFi enabled kissing machines designed to facilitate long-distance intimacy).- Barry Kripke has a speech impediment called rhotacism (he pronounces the letters "R" and "L" as "W"). Fellow Warner Brothers character Elmer Fudd has the same speech impediment.- Usually once a season we either learn of or we get to meet a retiring (or forcefully retired) wacky professor, which usually means their office space will soon be available.- In the first two seasons an unknown patron of Stewart's comic shop is referred to by the guys (and sometimes directly) by the name Captain Sweatpants.- Raj often makes racist jokes about India and then proceeds to tell the guys it isn't racist if he says it because he is from India.- Despite moving to California 6 years ago to pursue an acting career Penny still works as a waitress at the Cheesecake Factory.- Penny often eats with the guys though she never pays for her food. Her share of the bill is usually paid by Leonard whether or not he and Penny are dating at the time.- At some point (presumably in Season 4), the group of friends (Penny, Leonard, Howard and Raj) bought Sheldon a book explaining human relationships. When Sheldon asks an obvious question about why two people would want to behave a certain way or why a person would do a certain thing for another person, one of the group will say, "Read the book we got you!" or "Seriously, you really need to read that book we got for you!"- Raj is a huge fan of actress Sandra Bullock. Whenever someone on the show disparages her or one of her movies he always comes to her defense, often with comments such as, "You know my girl Sandy B always brings it!"- Leonard and Sheldon often comment about the other's mother as an example of how they wish they were raised (e.g. Leonard would've preferred Mary Cooper's doting care and Sheldon would've preferred Beverly Hofstadter's cold, detached method of parenting.)- Penny always mooches off of Leonard and Sheldon's WiFi signal. As a result Sheldon constantly changes the password to a passive-aggressive message for Penny such as "pennyisafreeloader" and "pennygetyourownwifi". The lock-out doesn't last long; when she asks Leonard for the password he always gives it to her, rendering Sheldon's efforts to force her to get her own internet connection completely futile.- Sheldon has what he refers to as a "germ phobia" when in actuality it is hypochondria coupled with obsessive-compulsive disorder. He is never farther than fifteen feet from a container of hand sanitizer, something he uses regularly. When he happens upon a container of hand sanitizer (as in a hospital or on a colleague's desk) he uses the opportunity to sanitize his hands.- Raj is considered the most handsome, well built, and wealthy of the group yet he is the only one that has never had a legitimate girlfriend. Despite suffering from selective mutism in the past, it has never been a factor in the ineffectiveness of creating or ending a relationship.- Howard almost always wears an alien head pin on his turtleneck/dickey collar. No one has ever made reference to the pin but it more than likely symbolizes Howard being an aerospace engineer/astronaut, both of which focus on space advancements.Sheldon is a self-proclaimed atheist, who frequently clashes with his deeply religious mother over the subject. However, when desperate, Sheldon often exclaims "Oh Lord", or appeals to the heavens nonetheless.
An ever growing list, but so far they include:- James Earl Jones voice of Darth Vader from the Star Wars franchise.- Carrie Fisher who portrayed Princess Leia Organa in the Star Wars franchise.- Katee Sackhoff from Battlestar Galactica- Michael Trucco from Battlestar Galactica- Leonard Nimoy and George Takei from the original Star Trek series and films.- Dakin Matthews who played Admiral Patterson on Star Trek: Voyager- Pasha D. Lychnikoff from the Star Trek 2009 remake.- Summer Glau from Terminator: The Sarah Connor Chronicles and Firefly- LeVar Burton , Brent Spiner and Wil Wheaton from Star Trek: The Next Generation- Margo Harshman and Angela Sargeant from Center of the Universe- Courtney Ford from True Blood- Ken Lerner and Jan Hoag of Buffy the Vampire Slayer- Eliza Dushku from Buffy the Vampire Slayer and Angel ,who also voiced Catwoman in Batman Year One.- Laurie Metcalf from ToyStory and Toystory 2, who voices Andy's mom and also appeared in 3rd Rock from the Sun. She also co-starred with Johnny Galecki in "Roseanne."- Famed Marvel Comics editor Stan Lee- Yeardley Smith from The Simpsons- Veteran voice-over actor Brian Posehn, from Scooby Doo! Abracadbra Doo! , Transformers:Antimated and the hit video game Halo 2- Comedian and veteran voice actor Howie Mandel of Lois & Clark: The New Adventures of Superman (as DC Comics supervillain Mister Mxyzptlk), voice of Gizmo in Gremlins. and voice of Bobby Generic from Bobby's World.- Diamond White from Transformers: Rescue Bots- Regina King who voices both Riley and Huey in The Boondocks- Comedian Lewis Black who voices Mr.E from Scooby Doo! Mystery Incorporated and Elliot/The Deadly Duplicator from Harvey Birdman, Attorney at Law.- Judy Greer from famed longtime comic strip turned tv series Archer.- Christine Baranski, from one of Chuck Lorre's first television shows Cybill, and also known from Speed Racer X who voiced both Spritle and Trixie- Danica McKellar (who also has a BS in Mathematics from UCLA), who has voiced many DC and Marvel comic characters such as Jubilee in the game X-men Legends, M'gann M'orzz of DC's Young Justice, Invisible Woman in the games Marvel Ultimate Alliance 2, and Marvel Ultimate Alliance. She also voices characters Lolla Cotgrove and Pona for the MMORPG EverQuest II.- Veteran video game voice actor Robert Clotworthy voice of the Stracraft video game franchise's Jim Raynor, and Marvel: Ultimate Alliance 2's Mr. Fantastic of the Fantastic Four.- Veteran video game voice actor Travis Davis of various games such as Command and Conquer 3, Resistance: Fall of Man, and Medal of Honor: Pacific Assault.- World famous British theoretical physicist and author Stephen Hawking- American NASA Astronaut Michael J. Massimino- American NASA Astronaut Buzz Aldrin- Nobel Prize winner and renowned physicist George Smoot- Famed astrophysicist Neil deGrasse Tyson- Famed American theoretical physicist and string theorist Brian Greene.- Apple Co-Founder Steve Wozniak- Ira Flatow host of Newton's Apple- Eventual costar Mayim Bialik, who earned a PhD in Neuroscience (as did her character) from UCLA.- Bill Nye, host of 90's science education show Bill Nye the Science Guy .(He appears in an episode guest starring Bob Newhart who, as Arthur Jeffries aka Professor Proton, parodies Don Herbert, the host of Mr. Wizard's World.)