The Big Bang Theory



The Big Bang Theory is an American television sitcom created by Chuck Lorre and Bill Prady, both of whom serve as executive producers on the series, along with Steven Molaro. All three also serve as head writers. The show premiered on CBS on September 24, 2007. The series' tenth season premiered on September 19, 2016. In March 2017, the series was renewed for two additional seasons, bringing its total to twelve, and running through the 2018–19 television season.

The show is primarily centered on five characters living in Pasadena, California: Leonard Hofstadter and Sheldon Cooper, both physicists at Caltech, who share an apartment; Penny, a waitress and aspiring actress who later becomes a pharmaceutical representative and who lives across the hall; and Leonard and Sheldon's similarly geeky and socially awkward friends and co-workers, aerospace engineer Howard Wolowitz and astrophysicist Raj Koothrappali. The geekiness and intellect of the four men are contrasted for comic effect with Penny's social skills and common sense.

Over time, supporting characters have been promoted to starring roles: Leslie Winkle, a physicist who dated Leonard and Howard; neuroscientist Amy Farrah Fowler, who joins the group after being matched to Sheldon on a dating website (and later becomes Sheldon's girlfriend); Bernadette Rostenkowski, Howard's wife (previously his girlfriend), a microbiologist and former part-time waitress alongside Penny; Stuart Bloom, the cash-strapped owner of the comic book store the characters often visit; and Emily Sweeney, a dermatologist who dated Raj.

Production
The structure of the original, unaired pilot, developed for the 2006–07 television season, was substantially different from the series' current form. The only characters retained in both pilots were Leonard (Johnny Galecki) and Sheldon (Jim Parsons), who are named after Sheldon Leonard. Althea (Vernee Watson) was a character featured in both pilots and the first series episode. Two female leads were Canadian actress Amanda Walsh as Katie, "a street-hardened, tough-as-nails woman with a vulnerable interior", and Iris Bahr as Gilda, a scientist colleague and friend of the male characters. Sheldon and Leonard meet Katie after she breaks up with a boyfriend and they invite her to share their apartment; Gilda is threatened by Katie's presence. Test audiences reacted negatively to Katie, but they liked Sheldon and Leonard. The original pilot used Thomas Dolby's hit "She Blinded Me with Science" as the theme song.

The series was not picked up, but the creators were given an opportunity to retool the show and produce a second pilot. They brought in the remaining cast and retooled the show to its final format. Katie was replaced by Penny (Kaley Cuoco). The original unaired pilot has never been officially released, but it has circulated on the Internet. On the evolution of the show, Chuck Lorre said, "We did the 'Big Bang Pilot' about two and a half years ago, and it sucked... but there were two remarkable things that worked perfectly, and that was Johnny and Jim. We rewrote the thing entirely and then we were blessed with Kaley and Simon and Kunal." As to whether the world will ever see the original pilot on a future DVD release, Lorre said, "Wow, that would be something, we will see. Show your failures..."

The first and second pilots of The Big Bang Theory were directed by James Burrows, who did not continue with the show. The reworked second pilot led to a 13-episode order by CBS on May 14, 2007. Prior to its airing on CBS, the pilot episode was distributed on iTunes free of charge. The show premiered on September 24, 2007, and was picked up for a full 22-episode season on October 19, 2007. The show is filmed in front of a live audience, and is produced by Warner Bros. Television and Chuck Lorre Productions. Production was halted on November 6, 2007, due to the Writers Guild of America strike. Nearly three months later, on February 4, 2008, the series was temporarily replaced by a short-lived sitcom, Welcome to the Captain. The series returned on March 17, 2008, in an earlier time slot and ultimately only 17 episodes were produced for the first season. After the strike ended, the show was picked up for a second season, airing in the 2008–2009 season, premiering in the same time slot on September 22, 2008. With increasing ratings, the show received a two-year renewal through the 2010–11 season in 2009. In 2011, the show was picked up for three more seasons. In March 2014, the show was renewed again for three more years through the 2016–17 season. Therefore, the series will at least reach 10 seasons. This marks the second time the series has gained a three-year renewal. In March 2017, the series was renewed for two additional seasons, bringing its total to 12, and running through the 2018–19 television season.

David Saltzberg, a professor of physics and astronomy at the University of California, Los Angeles, checks scripts and provides dialogue, mathematics equations, and diagrams used as props. According to executive producer/co-creator Bill Prady, "We're working on giving Sheldon an actual problem that he's going to be working on throughout the [first] season so there's actual progress to the boards...We worked hard to get all the science right."

Several of the actors in The Big Bang Theory previously worked together on Roseanne, including Johnny Galecki, Sara Gilbert, Laurie Metcalf (who plays Sheldon's mother, Mary Cooper), and Meagen Fay (who plays Bernadette's mother). Additionally, Lorre was a writer on the series for several seasons.

Theme song
The Canadian alternative rock band Barenaked Ladies wrote and recorded the show's theme song, which describes the history and formation of the universe and the Earth. Co-lead singer Ed Robertson was asked by Lorre and Prady to write a theme song for the show after the producers attended one of the band's concerts in Los Angeles. By coincidence, Robertson had recently read Simon Singh's book Big Bang, and at the concert, he improvised a freestyle rap about the origins of the universe. Lorre and Prady phoned Robertson shortly thereafter and asked him to write the theme song. Having been asked to write songs for other films and shows, but ending up being rejected because of producer's favor of other artist's song, Robertson agreed to write the theme only after learning that Lorre and Prady had not asked anyone else.

On October 9, 2007, a full-length (1 minute and 45 seconds) version of the song was released commercially. Although some sources identify the song title as "History of Everything", the cover art for the single identifies the title as "Big Bang Theory Theme". A music video was also released via special features on The Complete Fourth Season DVD and Blu-ray set. The theme was included on the band's greatest hits album, Hits from Yesterday & the Day Before, which was released on September 27, 2011. In September 2015, TMZ uncovered court documents showing that Steven Page sued former bandmate Robertson over the song, alleging that he was promised 20% of the proceeds, but that Robertson has kept that money entirely for himself.

Actors' salaries
For the first three seasons, Galecki, Parsons, and Cuoco, the three main stars of the show, received at most $60,000 per episode. The salary for the three went up to $200,000 per episode for the fourth season. Their per-episode pay went up an additional $50,000 in each of the following three seasons, culminating in $350,000 per episode in the seventh season. In September 2013, Bialik and Rauch renegotiated the contracts they held since they were introduced to the series in 2010. On their old contracts, each was making $20,000–$30,000 per episode, while the new contracts doubled that, beginning at $60,000 per episode, increasing steadily to $100,000 per episode by the end of the contract, as well as adding another year for both.

By season seven, Galecki, Parsons, and Cuoco were also receiving 0.25% of the series' back-end money. Before production began on the eighth season, the three plus Helberg and Nayyar, looked to renegotiate new contracts, with Galecki, Parsons, and Cuoco seeking around $1 million per episode, as well as more back-end money. Contracts were signed in the beginning of August 2014, giving the three principal actors an estimated $1 million per episode for three years, with the possibility to extend for a fourth year. The deals also include larger pieces of the show, signing bonuses, production deals, and advances towards the back-end. Helberg and Nayyar were also able to renegotiate their contracts, giving them a per-episode pay in the "mid-six-figure range", up from around $100,000 per episode they each received in years prior. The duo, who were looking to have salary parity with Parsons, Galecki, and Cuoco, signed their contracts after the studio and producers threatened to write the characters out of the series if a deal could not be reached before the start of production on season eight. By season 10, Helberg and Nayyar reached the $1 million per episode parity with Parsons, Galecki, and Cuoco, due to a clause in their deals signed in 2014.

In March 2017, the main cast members (Galecki, Parsons, Cuoco, Helberg, and Nayyar) took a 10% pay cut so Bialik and Rauch could increase their earnings from $100,000 per episode to $450,000. This put Galecki, Parsons, Cuoco, Helberg and Nayyar at $900,000 per episode, with Parsons, Galecki and Helberg also receiving overall deals with Warner Bros. Television. By the end of April, Bialik and Rauch had signed deals to earn $500,000 per episode, each, with the deals also including a separate development component for both actors. The deal was an increase from the $175,000 - $200,000 the duo had been making per episode.

Cast and characters
These actors are credited in all episodes of the series:
 * Leonard Hofstadter (portrayed by Johnny Galecki) is an experimental physicist with an IQ of 173, who received his PhD when he was 24 years old. His mother, Beverly (Christine Baranski), is cold and distant, a neuroscientist and psychiatrist who provided little, if any, nurturing when Leonard was growing up. Like all of the other major male characters, Leonard is a nerd who loves video games, comic books, and Dungeons & Dragons. Leonard is also lactose intolerant. The straight man of the series, he shares an apartment in Pasadena with Sheldon. Leonard is smitten with his neighbor Penny when they first meet. They briefly date at the end of season 1 and the start of season 2, taking a break before beginning a stable romantic relationship in season 3. However, they break up at the end of season 3 when Leonard tells Penny he loves her and she is unprepared to reciprocate. Leonard also briefly dates Leslie Winkle (Sara Gilbert) and Stephanie Barnett (Sara Rue) in season 2, and in season 4, he becomes seriously involved with Raj's sister Priya (Aarti Mann), a successful lawyer, but she eventually returns to India and they break up in season 5 when she admits to having cheated on him. Leonard and Penny again begin a romantic relationship in season 5 and they eventually marry in season 9.
 * Sheldon Cooper (portrayed by Jim Parsons) is originally from Galveston, Texas. Sheldon was a child prodigy with an eidetic memory who began college at the age of eleven (after completing the fifth grade), started graduate studies at age fourteen, and earned a PhD at age sixteen. A theoretical physicist researching quantum mechanics and string theory, he has two doctoral degrees: PhD and ScD. However, despite his IQ of 187, he finds many routine aspects of social situations and life in general difficult to grasp and navigate. His father died when he was fourteen, and his mother, Mary (Laurie Metcalf), is a devout Christian. He also has a twin sister, Missy (Courtney Henggeler), who does not share any of her brother's intellectual gifts. Sheldon has traditionally had a poor grasp of others' feelings, and little or no comprehension of nuance, often questioning others if a comment is intended as sarcasm. As a result, he is often extremely tactless and acts wildly inappropriately much of the time. He is determined to have his own way, boasts of his superior intelligence, and belittles his friends' accomplishments, making him appear petty and childlike. Sheldon has an extremely ritualized way of living (such as always sitting in the same spot on the sofa, or knocking on a door three times, each time saying the name of the person whom he is addressing) and a compulsion to complete things. He is also wary of germs and dislikes physical contact. Despite all these quirks, he begins a relationship with Amy Farrah Fowler in season 4. She officially becomes his girlfriend during season 5.
 * Penny Hofstadter (portrayed by Kaley Cuoco) is an aspiring actress from a town outside of Omaha, Nebraska. Penny moves in across the hall from Sheldon and Leonard in the series premiere. She attends casting calls and auditions, but is not very successful. To pay her bills, she waits and occasionally tends the bar at the Cheesecake Factory, although she often relies on the guys for free food, Wi-Fi and help paying her rent. After giving up hope of ever becoming a successful actress, Penny quits her job in season 7, and in season 8, she becomes a pharmaceutical sales representative with Zangen. This job finally allows her to gain financial independence. Penny attended, but did not graduate from, community college (She briefly goes back to school in season 6). She, however, has far more common sense and social awareness than the rest of the gang. Penny is also untidy and frequently consumes alcohol. Her maiden surname has never been revealed. In season 1, she dates Mike (Andrew Walker), whom she later dumps after he posts details about their sex life on his blog. She briefly dates comic book store owner Stuart Bloom in season 2, and during seasons 3 and 4, she dates Zack Johnson (Brian Thomas Smith), a handsome and friendly yet dim-witted guy, whom she married in Las Vegas, although they didn't think weddings in Las Vegas were real. In season 4, Penny becomes close friends with Bernadette and Amy, and they often hang out in each other's apartments or go out together. Penny also has a close friendship with Sheldon, despite his quirks. After a brief date at the end of season 1, and a relationship and break-up in season 3, Penny and Leonard form a relationship in season 5 and eventually marry in season 9. Kaley Cuoco began being credited as Kaley Cuoco-Sweeting starting with the season 7 episode The Convention Conundrum following her marriage to tennis player Ryan Sweeting. Following the announcement of her divorce from Sweeting in 2015, Cuoco's name during the opening credits was reverted to its original name in the season 9 episode The Bachelor Party Corrosion.
 * Howard Wolowitz (portrayed by Simon Helberg) is an aerospace engineer. Howard is Jewish and lives with his mother, Debbie (Carol Ann Susi). His father left both of them when Howard was eleven and has not been heard from since, with the exception of a letter on Howard's eighteenth birthday, which he refused to open. In season 8, he discovers he has a half-brother, Josh (Matt Bennett). Unlike Sheldon, Leonard, and Raj, Howard lacks a doctorate, earning him Sheldon's scorn. He defends this by pointing out that he has a master's degree in engineering from the elite Massachusetts Institute of Technology and that the apparatuses he designs are launched into space, unlike the purely abstract work of his friends. He himself goes into space at the end of season 5, training as an astronaut and serving as a payload specialist on the International Space Station. He has a marked sense of humor, which Leonard and Raj occasionally appreciate. In the early seasons of the show, Howard fancies himself a womanizer and devises outrageous pickup lines, which have limited success with women. In season 3, he starts dating Bernadette, and although they break up off screen, they later get back together and then get engaged in season 4 and married at the end of season 5. In season 6, Howard finally moves out of his mother's house and moves in with Bernadette. Howard also has a tendency to waste money on toys and often argues with Bernadette over money because of his oddly low income as an engineer and her high income as a pharmaceutical biochemist, resulting in Bernadette often giving Howard allowances (which Howard calls a stipend). In season 8, Howard's mother dies (following actress Carol Ann Susi's real life death in 2014), leaving him devastated. He and Bernadette later move into her home.
 * Rajesh Koothrappali (portrayed by Kunal Nayyar) is from New Delhi and is a particle astrophysicist at Caltech. Raj's family is very wealthy. Over the course of the series, he communicates with his parents, Dr. and Mrs. V.M. Koothrappali (Brian George and Alice Amter) via webcam. Raj is bashful around women and is unable to talk to them for the first six seasons (except for his mother and his sister) unless he drinks alcohol (or at least thinks he has drunk it) or takes an experimental medication. Unfortunately, the former causes him to behave outrageously and unpredictably, while the latter causes unforeseen side effects. Even so, he often has better luck with women than his overly-confident best friend, Howard. Raj also 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. In season 4, his sister Priya stays with him and becomes Leonard's girlfriend (much to Raj's annoyance). In season 6, Raj meets Lucy (Kate Micucci), who also suffers from social anxiety and they begin a relationship. However, Lucy ends the relationship, as she feels pressured when Raj wants her to meet his friends. Afterwards, a heartbroken Raj finally speaks to Penny without having consumed alcohol and overcomes his selective mutism. In season 7, he begins dating Emily and their relationship later becomes exclusive. Raj also has a Yorkshire Terrier named Cinnamon and the gang often joke about how unusually close he is with his dog.

These actors were first credited as guest stars and later promoted to main cast:
 * Sara Gilbert as Leslie Winkle (recurring season 1, starring season 2, guest star seasons 3 and 9) – a physicist who works in the same lab as Leonard. In appearance, she is essentially Leonard's female counterpart, wearing 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 calls him "dumbass", and usually bests him in their repartee. Leslie has casual sex with Leonard and later Howard. Gilbert and Galecki played the on-screen couple of Darlene Conner and David Healy in Roseanne some two decades earlier. Gilbert was promoted to a main cast member during the second season, but was demoted back to guest star status because producers could not come up with enough material for the character. Gilbert left the series after season 3 to focus her efforts on The Talk, on which she serves as executive producer for CBS. Gilbert returned for the series' 200th episode.
 * Melissa Rauch as Bernadette Rostenkowski-Wolowitz (recurring season 3, starring since season 4) is a young woman with a high-pitched voice who is initially a co-worker of Penny's, paying her way through graduate school, where she is studying microbiology. Bernadette is of Polish origin and was raised Catholic. Her father Mike (Casey Sander, who played Wade on Grace Under Fire) is a tough retired police officer and she has four other siblings. Bernadette is introduced to Howard by Penny as a result of an agreement between Howard and Leonard that if either ever ended up with a hot girlfriend, he would get the girlfriend to introduce the other to "a hot chick." At first, they do not get along, apparently having nothing in common, until they find out that they both have overbearing mothers. During season 3, they date and then break up off-screen. They get back together and get engaged in season 4 and marry at the end of season 5. She gives birth to Halley in season 10. After successfully defending her doctoral thesis, she lands a high-paying research position with Zangen at the end of season 4 (her high income becomes a source of conflict between her and Howard in later seasons). Although generally a sweet and good-natured person, Bernadette has a short fuse and can be vindictive and lash out when provoked, often sounding like Howard's mother and intimidating her colleagues. She is also shown to have a competitive streak.
 * Mayim Bialik as Amy Farrah Fowler (guest star season 3, starring since mid-season 4) is a woman selected by an online dating site as Sheldon's perfect mate after Raj and Howard secretly set up an account using Sheldon's information, prompting Raj to comment, "We finally have proof that aliens walk among us!" Amy is from Glendale and is a fan of Little House on the Prairie. While she and Sheldon initially share social cluelessness, after befriending Penny and Bernadette, Amy eventually becomes more interested in social and romantic interaction and is more socially aware than Sheldon. 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 to the point where Sheldon considers her his girlfriend and tells her that he loves her. Amy's sexual frustration in her relationship with Sheldon is a recurring topic in the series. Amy also believes she and Penny are best friends ("besties," as she puts it), a sentiment that Penny does not initially share. Penny eventually becomes a real friend, overlooking Amy's Sheldon-like qualities. Amy's admiration for Penny has at times bordered on physical attraction. Amy has a PhD in neurobiology (Bialik herself has a doctorate in neuroscience) and frequently uses monkeys in her research and experiments.
 * Kevin Sussman as Stuart Bloom (recurring seasons 2–5 and 7, starring seasons 6 and since season 8) is the mild-mannered, under-confident owner of a comic book store that the guys frequent. A brilliant artist, Stuart is a graduate of the prestigious Rhode Island School of Design, and though he is socially awkward, he possesses slightly better social skills than the rest of the guys. Unlike them, he is not a techno-geek. During Stuart's first appearance, the guys bring Penny along to the store, and he manages to ask her on a date. They go out a few times, until Penny mistakenly calls him "Leonard" while they are making out, leaving him devastated. In season 4, Stuart implies he is in financial trouble and that the comic book store is now also his home. At Howard's bachelor party, Stuart uses his toast to tell Howard how lucky he is and compares it to his own situation of living in the back of his store. In season 6, he is invited to join the guys' group while Howard is in space. At the end of season 7, the comic book store burns down, and he gets a new job caring for Howard's mother. The two become close and develop a strange relationship. Stuart moves into the Wolowitz house, much to the annoyance of Howard. He also briefly dates Howard's second cousin Jeanie (Kara Luiz), to whom Howard lost his virginity. After Mrs. Wolowitz's death in season 8, Stuart continues to live in her home, along with Howard and Bernadette, until he finds a place of his own in season 9.
 * Laura Spencer as Emily Sweeney (recurring seasons 7–8, starring season 9) is a dermatologist at Huntington Hospital who Raj finds on an online dating site. Emily went to Harvard and has a slightly alarming personality; she delights in the macabre and states that she likes her job because she can cut things with knives and likes Sally from The Nightmare Before Christmas (whom she has a tattoo of on her shoulder) because she has lots of scars and her limbs had to be sewn back on. Prior to meeting Raj, Emily was set up on a blind date with Howard. He came to her apartment with food poisoning, ruined her bathroom and escaped out the window (Emily nicknames Howard "Clogzilla"). In season 7, after finding Emily's online dating profile, Raj has Amy contact her as his wingman instead. Raj barges in on Emily and Amy and becomes weirded out and leaves. Raj later bumps into Emily and she agrees to give him another chance. At the end of season 7, their relationship becomes exclusive. Emily shows a slight dislike towards Penny as she previously and drunkenly almost hooked up with Raj in season 4. In the season 9 episode "The Valentino Submergence", Raj breaks up with Emily when he becomes infatuated with bartender and aspiring screenwriter, Claire (Alessandra Torresani). Then, after Emily leaves a gift for Raj, he goes to her apartment and they sleep together in "The Application Deterioration". Raj confirms they're still broken up in season 10, episode 5, "The Hot Tub Contamination".

Scientist cameos
As the theme of the show revolves around science, many distinguished and high-profile scientists have appeared as guest stars on the show. Famous astrophysicist and Nobel laureate George Smoot had a cameo appearance in episode 17 "The Terminator Decoupling", of the second season. Theoretical physicist Brian Greene also appeared on the show in "The Herb Garden Germination". Astrophysicist, science populizer, and physics outreach specialist, Neil deGrasse Tyson appeared in "The Apology Insufficiency". Cosmologist Stephen Hawking made a short guest appearance in the fifth-season episode "The Hawking Excitation" on April 5, 2012. In the episode, he meets Sheldon and points out a mistake in Sheldon's new Higgs boson analysis. Hawking also speaks on the phone at the end of the episode "The Extract Obliteration" with Sheldon but is not seen on-camera.

In season 8 episode 14, Hawking video-conferences with Sheldon and Leonard after trolling their joint paper online. Hawking makes another appearance through a video call in season 9 episode 17 named 'The Celebration Experimentation' (the 200th episode). In the end of season 5 and the beginning of season 6, NASA astronaut Michael J. Massimino played himself multiple times in the role of Howard's fellow astronaut. In season 7, Bill Nye appears in an episode ("The Proton Displacement") in which Sheldon feels slighted by his childhood science hero, Professor Proton, hiring Bill to fill the void. Elon Musk appears in season 9's "The Platonic Permutation," where he and Howard volunteer at a homeless shelter on Thanksgiving.

Science
Much of the series focuses on science, particularly physics. The four main male characters are employed at Caltech and have science-related occupations, as do Bernadette and Amy. The characters frequently banter about scientific theories or news (notably around the start of the show), and make science-related jokes.

Science has also interfered with the characters' romantic lives. Leslie breaks up with Leonard when he sides with Sheldon in his support for string theory rather than loop quantum gravity. When Leonard joins Sheldon, Raj, and Howard on a three-month Arctic research trip, it separates Leonard and Penny at a time their relationship is budding. When Bernadette takes an interest in Leonard's work, it makes both Penny and Howard envious and results in Howard confronting Leonard, and Penny asking Sheldon to teach her physics. Sheldon and Amy also briefly end their relationship after an argument over which of their fields is superior.

David Saltzberg, who has a PhD in physics, has served as the science consultant for the show for six seasons and attends every taping. While Saltzberg knows physics, he sometimes needs assistance from Mayim Bialik, who has a PhD in neuroscience. Saltzberg sees early versions of scripts which need scientific information added to them, and he also points out where the writers, despite their knowledge of science, have made a mistake. He is usually not needed during a taping unless a lot of science, and especially the whiteboard, is involved.

Science fiction media
The four main male characters are all avid science fiction, fantasy, and comic book fans and memorabilia collectors.

Star Trek in particular is frequently referenced and Sheldon identifies strongly with the character of Spock, so much so that when he is given a used napkin signed by Leonard Nimoy as a Christmas gift from Penny he is overwhelmed with excitement and gratitude ("I possess the DNA of Leonard Nimoy?!"). Star Trek: The Original Series cast member George Takei has made a cameo, and Leonard Nimoy made a cameo as the voice of Sheldon's vintage Mr. Spock action figure (both cameos were in dream sequences). Star Trek: The Next Generation cast members Brent Spiner and LeVar Burton have had cameos as themselves, while Wil Wheaton has a recurring role as a fictionalized version of himself.

They are also fans of Star Wars, Battlestar Galactica, and Doctor Who. In the episode "The Ornithophobia Diffusion", when there is a delay in watching Star Wars on Blu-ray, Howard complains, "If we don't start soon, George Lucas is going to change it again" (referring to Lucas' controversial alterations to the films) and in "The Hot Troll Deviation", Katee Sackhoff of Battlestar Galactica appeared as Howard's fantasy dream girl. The characters have different tastes in franchises with Sheldon praising Firefly but disapproving of Leonard's enjoyment of Babylon 5. With regard to fantasy, the four make frequent references to The Lord of the Rings and Harry Potter novels and movies. Additionally, Howard can speak Sindarin, one of the two Elvish languages from The Lord of the Rings.

Wednesday night is the group's designated "comic book night" because that is the day of the week when new comic books are released. The comic book store is run by fellow geek and recurring character Stuart. On a number of occasions, the group members have dressed up as pop culture characters, including The Flash, Aquaman, Frodo Baggins, Superman, Batman, Spock, The Doctor, Green Lantern, and Thor. As a consequence of losing a bet to Stuart and Wil Wheaton, the group members are forced to visit the comic book store dressed as Catwoman, Wonder Woman, Batgirl, and Supergirl. DC Comics announced that, to promote its comics, the company will sponsor Sheldon wearing Green Lantern T-shirts.

Various games have been featured, as well as referenced, on the series (e.g. World of Warcraft, Halo, Mario, etc.), including fictional games like Mystic Warlords of Ka'a (which became a reality in 2011) and Rock-paper-scissors-lizard-Spock.

Leonard and Penny's relationship
One of the recurring plot lines is the relationship between Leonard and Penny. Leonard becomes attracted to Penny in the pilot episode and his need to do favors for her is a frequent point of humor in the first season. Their first long term relationship begins when Leonard returns from a three-month expedition to the North Pole in the season 3 premiere. However, when Leonard tells Penny that he loves her, she realizes she cannot say it back. Both Leonard and Penny go on to date other people; most notably with Leonard dating Raj's sister Priya for much of season 4. This relationship is jeopardized when Leonard comes to falsely believe that Raj has slept with Penny, and ultimately ends when Priya sleeps with a former boyfriend in "The Good Guy Fluctuation".

Penny, who admits to missing Leonard in "The Roommate Transmogrification", accepts his request to renew their relationship in "The Beta Test Initiation". After Penny suggests having sex in "The Launch Acceleration", Leonard breaks the mood by proposing to her. Penny says "no" but does not break up with him. She stops a proposal a second time in "The Tangible Affection Proof". In the sixth-season episode, "The 43 Peculiarity", Penny finally tells Leonard that she loves him. Although they both feel jealousy when the other receives significant attention from the opposite sex, Penny is secure enough in their relationship to send him off on an exciting four-month expedition without worrying in "The Bon Voyage Reaction". After Leonard returns, their relationship blossoms over the seventh season. In the penultimate episode "The Gorilla Dissolution", Penny admits that they should marry and when Leonard realizes that she is serious, he proposes with a ring that he had been saving for years. Leonard and Penny decide to elope to Las Vegas in the season 8 finale, but beforehand, wanting no secrets, Leonard admits to kissing another woman, Mandy Chow (Melissa Tang) while on an expedition on the North Sea. Despite this, Leonard and Penny finally elope in the season 9 premiere.

Sheldon and Amy's relationship
In the third-season finale, Raj and Howard search for a woman compatible with Sheldon and discover neurobiologist Amy Farrah Fowler. Like him, she has a history of social ineptitude and participates in online dating only to fulfill an agreement with her mother. This spawns a storyline in which Sheldon and Amy communicate daily while insisting to Leonard and Penny that they are not romantically involved. In "The Agreement Dissection", Sheldon and Amy talk in her apartment after a night of dancing and she kisses him on the lips. Instead of getting annoyed, Sheldon says "fascinating" and later asks Amy to be his girlfriend in "The Flaming Spittoon Acquisition". The same night he draws up "The Relationship Agreement" to verify the ground rules of him as her boyfriend and vice versa (similar to his "Roommate Agreement" with Leonard). Amy agrees but later regrets not having had a lawyer read through it.

In the episode "The Launch Acceleration", Amy tries to use her "neurobiology bag of tricks" to increase the attraction between herself and Sheldon. In the final fifth-season episode "The Countdown Reflection", Sheldon takes Amy's hand as Howard is launched into space. In the sixth season first episode "The Date Night Variable", after a dinner in which Sheldon fails to live up to this expectation, Amy gives Sheldon an ultimatum that their relationship is over unless he tells her something from his heart. Amy accepts Sheldon's romantic speech even after learning that it is a line from the first Spider-Man movie. In "The Cooper/Kripke Inversion" Sheldon states that he has been working on his discomfort about physical contact and admits that "it's a possibility" that he could one day have sex with Amy. Amy is revealed to have similar feelings in "The Love Spell Potential". Sheldon explains that he never thought about intimacy with anyone before Amy.

"The Locomotive Manipulation" is the first episode in which Sheldon initiates a kiss with Amy. Although initially done in a fit of sarcasm, he discovers that he enjoys the feeling. Consequently, Sheldon slowly starts to open up over the rest of the season, and starts a more intimate relationship with Amy. However, in the season finale, Sheldon leaves temporarily to cope with several changes and Amy becomes distraught. However, in "The Prom Equivalency" he hides in his room to avoid going to a mock prom reenactment with her. In the resulting stand-off, Amy is about to confess that she loves Sheldon, but he surprises her by saying that he loves her too. This prompts Amy to have a panic attack.

In the season eight finale, Sheldon and Amy get into a fight about commitment on their 5-year anniversary. Amy tells Sheldon that she needs to think about the future of their relationship, unaware that Sheldon was about to propose to her. Season nine sees Sheldon harassing Amy about making up her mind until she breaks up with him. Both struggle with singlehood and trying to be friends for the next few weeks until they reunite in episode ten and have sex for the first time on Amy's birthday.

Howard's mother
In scenes set at Howard's home, he interacts with his rarely-seen mother (voiced by Carol Ann Susi until her death) by shouting from room to room in the house. She similarly interacts with other characters in this manner. She reflects the Jewish mother stereotype in some ways, such as being overly controlling of Howard's adult life and sometimes trying to make him feel guilty about causing her trouble. She is dependent on Howard, as she requires him to help her with her wig and makeup in the morning. Howard in turn is attached to his mother to the point where she still cuts his meat for him, takes him to the dentist, does his laundry and "grounds" him when he returns home after briefly moving out. Until Howard's marriage to Bernadette in the fifth-season finale, Howard's former living situation led Leonard's psychiatrist mother to speculate that he may suffer from some type of pathology, and Sheldon to refer to their relationship as Oedipal. In season 8, Howard's mother dies in her sleep while in Florida, which devastates Howard and Stuart, who briefly lived with Mrs. Wolowitz.

Vanity cards
Like most shows created by Chuck Lorre, The Big Bang Theory ends by showing a vanity card written by Lorre after the credits, followed by the Warner Bros. Television closing logo. These cards are archived on Lorre's website.

The Theorists
Through the use of his vanity cards at the end of episodes, Lorre alleged that the program had been plagiarized by a show produced and aired in Belarus. Officially titled Теоретики (The Theorists), the show features "clones" of the main characters, a similar opening sequence, and what appears to be a very close Russian translation of the scripts. Lorre expressed annoyance and described his inquiry with the Warner Bros. legal department about options. The television production company and station's close relationship with the Belarus government was cited as the reason that any attempt to claim copyright infringement would be in vain because the company copying the episodes is operated by the government.

However, no legal action was required to end production of the other show: as soon as it became known that the show was unlicensed, the actors quit and the producers cancelled it. Dmitriy Tankovich (who plays Leonard's counterpart, "Seva") said in an interview, "I'm upset. At first, the actors were told all legal issues were resolved. We didn't know it wasn't the case, so when the creators of The Big Bang Theory started talking about the show, I was embarrassed. I can't understand why our people first do, and then think. I consider this to be the rock bottom of my career. And I don't want to take part in a stolen show".

Critical reception
In 2013, TV Guide ranked the series #52 on its list of the 60 Best Series of All Time. The review aggregation website Rotten Tomatoes reported a 55% approval rating for the first season based on reviews from 22 critics, with an average rating of 5.18/10. The website's critical consensus reads, "The Big Bang Theory brings a new class of character to mainstream television, but much of the comedy feels formulaic and stiff." On Metacritic, the season holds a score of 57 out of 100, based on reviews from 23 critics, indicating "mixed or average reviews".

U.S. standard ratings
The Big Bang Theory started off slowly in the ratings, failing to make the top 50 in its first season (ranking 68th), and ranking 40th in its second season. When the third season premiered on September 21, 2009, however, The Big Bang Theory ranked as CBS's highest-rated show of that evening in the adults 18–49 demographic (4.6/10) along with a then-series-high 12.83 million viewers. After the first three seasons aired at different times on Monday nights, CBS moved the show to Thursdays at 8:00 ET for the 2010–2011 schedule, to be in direct competition with NBC's Comedy Block and Fox's American Idol (then the longest reigning leading primetime show on U.S. television from 2004 to 2011). During its fourth season, it became television's highest rated comedy, just barely beating out eight-year champ Two and a Half Men. However, in the age 18–49 demographic (the show's target age range), it was the second highest rated comedy, behind ABC's Modern Family. The fifth season opened with viewing figures of over 14 million.

The sixth season boasts some of the highest-rated episodes for the show so far, with a then-new series high set with "The Bakersfield Expedition", with 20 million viewers, a first for the series, which along with NCIS, made CBS the first network to have two scripted series reach that large an audience in the same week since 2007. In the sixth season, the show became the highest rated and viewed scripted show in the 18–49 demographic, trailing only the live regular NBC Sunday Night Football coverage, and was third in total viewers, trailing NCIS and Sunday Night Football. Season seven of the series opened strong, continuing the success gained in season six, with the second episode of the premiere, "The Deception Verification", setting the new series high in viewers with 20.44 million.

Showrunner Steve Molaro, who took over from Bill Prady with the sixth season, credits some of the show's success to the sitcom's exposure in off-network syndication, particularly on TBS, while Michael Schneider of TV Guide attributes it to the timeslot move two seasons earlier. Chuck Lorre and CBS Entertainment president Nina Tassler also credit the success to the influence of Molaro, in particular the deepening exploration of the firmly established regular characters and their interpersonal relationships, such as the on-again, off-again relationship between Leonard and Penny. Throughout much of the 2012–13 season, The Big Bang Theory placed first in all of syndication ratings, receiving formidable competition from only Judge Judy and Wheel of Fortune (first-run syndication programs). By the end of the 2012–13 television season, The Big Bang Theory had dethroned Judge Judy as the ratings leader in all of syndicated programming with 7.1, Judy descending to second place for that season with a 7.0. The Big Bang Theory did not place first in syndication ratings for the 2013–14 television season, beaten out by Judge Judy.

UK distribution and ratings
The show made its United Kingdom debut on Channel 4 on February 14, 2008. The show was also shown as a 'first-look' on Channel 4's digital offshoot E4 prior to the main channel's airing. While the show's ratings were not deemed strong enough for the main channel, they were considered the opposite for E4. For each following season, all episodes were shown first-run on E4, with episodes only aired on the main channel in a repeat capacity, usually on a weekend morning. From the third season, the show aired in two parts, being split so that it could air new episodes for longer throughout the year. This was due to rising ratings. The first part began airing on December 17, 2009 at 9:00 p.m. while the second part, containing the remaining eleven episodes, began airing in the same time period from May 6, 2010. The first half of the fourth season began airing on November 4, 2010, at 9:00 p.m., drawing 877,000 viewers, with a further 256,000 watching on the E4+1 hour service. This gave the show an overall total of 1.13 million viewers, making it E4's most watched programme for that week. The increased ratings continued over subsequent weeks.

The fourth season's second half began on June 30, 2011. Season 5 began airing on November 3, 2011 at 8:00 p.m. as part of E4's Comedy Thursdays, acting as a lead-in to the channel's newest comedy, Perfect Couples. Episode 19, the highest-viewed episode of the season, attracted 1.4 million viewers. Season 6 premiered on November 15, 2012, with 1.89 million viewers and a further 469,000 on the time shift channel, bringing the total to 2.31 million, E4's highest viewing ratings of 2012, and the highest the channel had received since June 2011. The sixth season returned in mid 2013 to finish airing the remaining episodes. Season 7 premiered on E4 on October 31, 2013 at 8:30pm and hit multiple ratings records this season. The second half of season seven aired in mid 2014. The eighth season premiered on E4 on October 23, 2014 at 8:30 p.m. During its eighth season, The Big Bang Theory shared its 8:30 p.m. time period with fellow CBS comedy, 2 Broke Girls. Following the airing of the first eight episodes of that show's fourth season, The Big Bang Theory returned to finish airing its eighth season on March 19, 2015.

Netflix UK & Ireland announced on February 13, 2016 that seasons 1–8 would be available to stream from February 15, 2016.

Canadian ratings
The Big Bang Theory started off quietly in Canada, but managed to garner major success in later seasons. The Big Bang Theory is telecast throughout Canada via the CTV Television Network in simultaneous substitution with cross-border CBS affiliates. Now immensely popular in Canada, The Big Bang Theory is also rerun daily on the Canadian cable channel The Comedy Network.

The season 4 premiere garnered an estimated 3.1 million viewers across Canada. This is the largest audience for a sitcom since the series finale of Friends (12.4 million viewers). The Big Bang Theory has pulled ahead and has now become the most-watched entertainment television show in Canada.

Broadcast
The Big Bang Theory premiered in the United States on September 24, 2007 on CBS. The series debuted in Canada on CTV in September 2007. On February 14, 2008, the series debuted in the United Kingdom on channels E4 and Channel 4. In Australia the first seven seasons of the series began airing on the Seven Network and 7mate from October 2015 and also gained the rights to season 8 in 2016, though the Nine Network has rights to air seasons nine & ten.

Syndication
In May 2010, it was reported that the show had been picked up for syndication, mainly among Fox's owned and operated stations and other local stations, with Warner Bros. Television's sister cable network TBS holding the show's cable syndication rights. Broadcast of old shows began airing in September 2011. TBS now airs the series in primetime on Tuesdays, Wednesdays, and Thursdays, with evening broadcasts on Saturdays (TBS's local sister station in Atlanta also holds local weeknight rights to the series). Although details of the syndication deal have not been revealed, it was reported the deal "set a record price for a cable off-network sitcom purchase". CTV holds national broadcast syndication rights in Canada, while sister cable network The Comedy Network holds cable rights.

Online media
Warner Bros. Television controls the online rights for the show. Full episodes are available at tv.com, while short clips and recently aired full episodes are available on cbs.com. In Canada, recent episode(s) and pictures are available on CTV.ca. After the show has aired in New Zealand the shows are available in full online at TVNZ's on demand web service.

Home media
The first and second seasons were only available on DVD upon their time of release in 2008 and 2009. Starting with the release of the third season in 2010 and continuing every year with every new season, a Blu-ray disc set has also been released in conjunction with the DVD. In 2012, Warner Bros. released the first two seasons on Blu-ray, marking the first time that all episodes were available on the Blu-ray disc format.

Awards and nominations
In August 2009, the sitcom won the best comedy series TCA award and Jim Parsons (Sheldon) won the award for individual achievement in comedy. In 2010, the show won the People's Choice Award for Favorite Comedy, while Parsons won a Primetime Emmy Award for Outstanding Lead Actor in a Comedy Series. On January 16, 2011, Parsons was awarded a Golden Globe for Best Performance by an Actor in a Television Series – Comedy or Musical, an award that was presented by co-star Kaley Cuoco. On September 18, 2011, Parsons was again awarded an Emmy for Best Actor in a Comedy Series. On January 9, 2013, the show won People's Choice Award for Favorite Comedy for a second time. August 25, 2014, Jim Parsons was awarded an Emmy for Best Actor in a Comedy Series. The Big Bang Theory also won the 2016 People's Choice Awards for under Favorite TV Show and Favorite Network TV Comedy with Jim Parsons winning Favorite Comedic TV Actor. On January 20, 2016, The Big Bang Theory also won the International category at the UK's National Television Awards.

Merchandise
On March 16, 2014, a Lego Ideas project portraying the living room scene in Lego style with the main cast as minifigures reached 10,000 supporters on the platform, which qualified it to be considered as an official set by the Lego Ideas review board. On November 7, 2014, Lego Ideas approved the design and began refining it. The set was released in August 2015, with an exclusive pre-sale taking place at the San Diego Comic-Con International.

Spin-off series
In November 2016, it was reported that CBS was in negotiations to create a spin-off of The Big Bang Theory centered on Sheldon as a young boy. The prequel series, described as "a Malcolm in the Middle-esque single-camera family comedy" would be executive produced by Lorre and Molaro, with Prady expected to be involved in some capacity, and intended to air in the 2017–18 season alongside The Big Bang Theory. The initial idea for the series came from Parsons, who passed it along to The Big Bang Theory producers. In early March 2017, Iain Armitage was cast as the younger Sheldon, as well as Zoe Perry as his mother, Mary Cooper. Perry is the real-life daughter of Laurie Metcalf, who portrays Mary Cooper on The Big Bang Theory.

On March 13, 2017, CBS ordered the spin-off Young Sheldon series. Jon Favreau will direct and executive produce the pilot. Created by Lorre and Molaro, the series follows 9-year-old Sheldon Cooper as he attends high school in East Texas. Alongside Armitage as 9-year-old Sheldon Cooper and Perry as Mary Cooper, Lance Barber stars as George Cooper, Sheldon's father; Raegan Revord stars as Missy Cooper, Sheldon's twin sister; and Montana Jordan as George Cooper, Sheldon's older brother. Jim Parsons reprises his role as adult Sheldon Cooper, as narrator for the series. Parsons, Lorre, Molaro and Todd Spiewak will also serve as executive producers on the series, for Chuck Lorre Productions, Inc. in association with Warner Bros. Television. It is scheduled to begin airing on November 2, 2017, after The Big Bang Theory. It will have a special preview on September 25, 2017.