The Big Bang Theory

Science
Much of the show focuses on science, particularly physics. The four main male characters are employed at Caltec and have science-related occupations. 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 broke up with Leonard when he sided with Sheldon in his support for string theory rather than her support forloop quantum gravity. When Leonard joined Sheldon, Raj, and Howard on a three-month Arctic research trip, it separated Leonard and Penny at a time their relationship was budding. When Bernadette took an interest in Leonard's work, it made both Penny and Howard jealous and resulted in Howard confronting Leonard, and Penny asking Sheldon to teach her physics. Sheldon and Amy also briefly ended their relationship after an argument over which of their fields was superior to the other's.

David Saltzberg, who has a Ph.D. in physics, has served as science consultant for the show for five seasons. While Salzberg knows physics, he sometimes needs assistance from Mayim Bialik, who has a Ph.D. in neuroscience. Salzberg 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 in a taping unless a lot of science, and especially the whiteboard, is involved.

[edit] Sci-fi, fantasy and comic book fandom
The four main male characters are all avid sci-fi, fantasy, and comic book fans and memorabilia collectors.

Star Trek in particular is frequently referenced and Sheldon identifies strongly with the character of Spock; 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 Generationcast members Brent Spiner and LeVar Burton have had cameos as themselves, while Wil Wheaton has a recurring role as a fictionalized version of himself All four male characters can speak Klingon to varying degrees—the opening of the episode "The Panty Piñata Polarization" shows them playing "Klingon Boggle". During the "The Launch Acceleration" episode, Amy and Sheldon were seen playing doctor with Amy dressed in a Star Trek medical uniform.

In addition to Star Trek, the group are also fans of Star Wars, Battlestar Galactica and Doctor Who; numerous quotes from Star Wars are made and references to Battlestar Galactica can be seen in some episodes. In season two, Raj once likens Sheldon to C-3PO,[56] an intelligent, yet semi-annoying protocol droid in the Star Wars series. In episode 5 of season 2, Sheldon wants to return a set of white Star Wars sheets to Pottery Barn as they are too exciting for sleeping in.[57] Leonard likes Babylon 5, but Sheldon refuses to watch it, calling it derivative.[episode needed] [note 1] Sheldon also expresses a great liking of Joss Whedon's Firefly, as he is shown to be quite upset with the Fox network for cancelling it.[note 1]

The four males are also a bit of fans of non-scientific fantasy and make references to The Lord of the Rings and Harry Potter. Howard can speak Sindarin, one of the two Elvishdialogues from The Lord of the Rings. In one episode, they find a prop of the One Ring and they all four fight over who gets to keep it. Leonard has a Frodo Baggins costume. Raj once bought a hand crafted Harry Potter wand on ebay.com and but instead got a stick. Howard once accused Sheldon of being a Muggle.

 Wednesday night is the group's designated "comic book store night", the store in question being 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 (albeit as the original Norse god and not the Marvel Comics character). As a consequence of losing a bet to Stuart, the group members are forced to visit the comic book store dressed as Catwoman, Wonder Woman , Batgirl , and Supergirl. [58] Sheldon often wears t-shirts depicting Batman, Superman, Flash, Greatest American Hero, or Green Lantern. DC Comics announced that, to promote its comics, the company will sponsor Sheldon wearing Green Lantern t-shirts. [59]

The characters are also fans of the Indiana Jones series, and willing to spend several hours in line outside of a theater to watch a special screening of Raiders of the Lost Ark with 21 seconds of new footage.

[edit] Leonard and Penny's relationship
<p style="line-height:19.200000762939453px;font-family:sans-serif;">One of the recurring topics is the relationship between Leonard and Penny. Leonard becomes attracted to Penny within seconds of seeing her in the pilot episode. The first season frequently featured Leonard's attraction to Penny as a basis for humor. Leonard and Penny go on a date that started the final episode of the first season and ended at the start of the second season; however, Penny quickly breaks up with Leonard because she is afraid that her educational attainments aren't good enough for Leonard and that he may become bored in "The Bad Fish Paradigm" episode. Her excuse for breaking with Leonard was when he showed her some brochures from a local community college and she took it as a knock against her education level and that she felt that he would only date a girl with a college education.

<p style="margin-top:0.4em;margin-bottom:0.5em;line-height:19.200000762939453px;font-family:sans-serif;">They both date other people throughout the second season, but clearly still have feelings for each other as when Penny admits this to herself in "The Monopolar Expedition". When Leonard returns from a 3-month expedition to the North Pole in the season 3 premiere, they commence a relationship which lasts for most of the season until Leonard tells Penny that he loves her and she realizes she cannot say it back, and she reluctantly breaks up with him after Wil Wheaton meddles with their relationship in order to beat Sheldon at bowling per "The Wheaton Recurrence". <p style="margin-top:0.4em;margin-bottom:0.5em;line-height:19.200000762939453px;font-family:sans-serif;">Again, both Leonard and Penny go on to date other people; most notably with Leonard dating Raj's sister Priya for much of season 4. Penny has shown regret towards her decision to break up with Leonard by admitting to her girlfriends that she misses Leonard.<sup class="noprint Inline-Template" style="line-height:1em;white-space:nowrap;">[episode needed] She also exhibits jealousy towards Priya, especially after Priya demands Leonard stay away from her as in "The Prestidigitation Approximation". After dating Leonard, Penny also has negative reactions to her male dates who are not very intelligent after dating Zack in "The Lunar Excitation".

<p style="margin-top:0.4em;margin-bottom:0.5em;line-height:19.200000762939453px;font-family:sans-serif;">Eventually, as the episodes rolled on, Leonard became more and more interested in Priya. However she seemed to become less and less interested in Leonard as they went on dating. Later in the season, Leonard is at Raj's apartment, making out with Priya, when her parents call from India, and she has Leonard leave the room as she answers the call. Unknowing of Leonard's presence or his secret relationship with Priya, her parents state that they will be so happy when Priya moves back to India in "The Roommate Transmogrification" episode. Leonard comes in, shouting out that he is shocked she is moving back to India, and assumes it means he and Priya are breaking up. Leonard goes home to his apartment, where Raj has been sleeping because of Leonard staying at Raj's apartment. Penny and Raj, while enjoying a friendly evening, got drunk and ended up in bed. Leonard assumes the worst when they emerge from his room, only to learn the truth later, that nothing happened.

<p style="margin-top:0.4em;margin-bottom:0.5em;line-height:19.200000762939453px;font-family:sans-serif;">In season five in "The Infestation Hypothesis", Leonard resumes his relationship with Priya online. It seems to work for Leonard, but he is conflicted when he meets Alice, a girl who is really into him, at the comic book store. Leonard decides he must be faithful to Priya, ending things with Alice. Leonard confesses to Priya about going out with Alice, only to discover that Priya has slept with an ex-boyfriend, and they break up in "The Good Guy Fluctuation".

<p style="margin-top:0.4em;margin-bottom:0.5em;line-height:19.200000762939453px;font-family:sans-serif;">Penny is still single and dating, though when drunk has confessed that she regrets breaking up with Leonard, as in "The Roommate Transmogrification". In "The Ornithophobia Diffusion", Leonard and Penny go to the movies as friends. Leonard decides that since they are no longer dating he can be honest and does not have to pay for everything or do whatever Penny wants to make Penny like him and have sex with him. The two bicker all evening and sabotage each other's attempts to chat up people in the bar. Penny decides that she likes the new, more assertive Leonard. Leonard sees this as another opportunity to grovel and try to get Penny to sleep with him, so she leaves. <p style="margin-top:0.4em;margin-bottom:0.5em;line-height:19.200000762939453px;font-family:sans-serif;">On the spur of the moment in "The Recombination Hypothesis", Leonard asks Penny out on a date after he imagined what getting back with her might be like. Their real date ends successfully, and they agree to try to renew their relationship slowly in "The Beta Test Initiation". They share a kiss. During her renewed relationship with Leonard she has dismissed comments about him ever leaving or dumping her or about worrying about his unfaithfulness around other women and strippers as in the episode "The Stag Convergence". After Penny suggested having sex in "The Launch Acceleration", Leonard breaks the mood by proposing to her. They later meet and Penny has the courage to tell him "no" and not break up with him as she did two years previously when he told her that he loved her in "The Wheaton Recurrence".

<p style="margin-top:0.4em;margin-bottom:0.5em;line-height:19.200000762939453px;font-family:sans-serif;">Showrunner Bill Prady has hinted that Leonard and Penny's relationship may get "rocky" in season six. Prady explained that the series' on-again-off-again couple will continue to face "challenges", such as their conflicting views about when to "settle down". "What we've always said about Penny and Leonard is they met each other at the wrong time in their lives," he told E!. "Leonard is ready to settle down and Penny isn't yet and it will make things rocky for a while. I think that until she grows up a little bit – and I don't mean emotionally, I mean chronologically – I think they have challenges [ahead]."

[edit] Sheldon and Amy's relationship
<p style="line-height:19.200000762939453px;font-family:sans-serif;">A new recurring subject starting at the end of the third season is the status of the relationship of Sheldon and Amy Farrah Fowler, Ph.D., a neurobiologist. Raj and Howard found her as a possible match for Sheldon through an internet dating service (without Sheldon's knowledge) in "The Lunar Excitation". By Sheldon's own admission, she is most like him by any standard to his mother in "The Zazzy Substitution". Like him, she has previously avoided relationships (whether romantic or otherwise is unclear), and only participated in the online dating herself to fulfill an agreement with her mother that she date at least once a year (in exchange, her mother does not discuss Amy's lack of a love life, plus she gains use of her mother's George Foreman Grill) as told to Penny on her date with Sheldon during "The Robotic Manipulation".

<p style="margin-top:0.4em;margin-bottom:0.5em;line-height:19.200000762939453px;font-family:sans-serif;">During the four months of their relationship (taking place off-screen between seasons 3 and 4), they communicated on a daily basis via text messages, email and Twitter, but never saw each other in person per "The Robotic Manipulation". Sheldon, however, did not consider Amy his girlfriend. Penny later suggests that they should go on a date and ends up driving them and having dinner with them in "The Robotic Manipulation." Penny occasionally refers to Sheldon and Amy collectively as "Shamy" as in "The Shiny Trinket Maneuver".

<p style="margin-top:0.4em;margin-bottom:0.5em;line-height:19.200000762939453px;font-family:sans-serif;">In "The Agreement Dissection", Amy, Penny, and Bernadette decide to take Sheldon dancing. Sheldon dances only with Amy, which he does not mind. He later follows Amy back to her apartment. They talk for a few minutes before she kisses him on the lips. Instead of getting annoyed, Sheldon just says "Fascinating." This is a catalyst for later events<sup class="Template-Fact" style="line-height:1em;white-space:nowrap;">[citation needed] and clash of personalities in the relationship of the more scientific, masculine Sheldon, and the more socially open, feminine, and annoyed Amy.

<p style="margin-top:0.4em;margin-bottom:0.5em;line-height:19.200000762939453px;font-family:sans-serif;">In "The Flaming Spittoon Acquisition", after Amy agrees to go on a date with Stuart the comic book store owner, Sheldon asks Amy to be his girlfriend interrupting her date with Stuart with the stipulation that no other changes occur in their current relationship. The same night and episode, he draws up "The Relationship Agreement" to verify the ground rules of him as her boyfriend and her as his girlfriend (similar to his "Roommate Agreement" with Leonard). Amy agrees but later regrets not having a lawyer read through it. <p style="margin-top:0.4em;margin-bottom:0.5em;line-height:19.200000762939453px;font-family:sans-serif;">After Penny and Bernadette go wedding shopping without Amy in "The Isolation Permutation", Sheldon comforts a depressed Amy by cuddling with her on her couch; however, Amy first suggests that they have sex.

<p style="margin-top:0.4em;margin-bottom:0.5em;line-height:19.200000762939453px;font-family:sans-serif;">In the episode "The Launch Acceleration", Amy says she’d like to do an experiment using her neurobiology bag of tricks to increase Sheldon’s feelings toward her. Sheldon is skeptical, but goes with it. Amy says she’d like to put on some romantic dinner music, and ends up putting on the Super Mario Bros. theme song. Sheldon catches on, and calls Amy out on the fact that she’s trying to engage his feelings of the happiest times of his life as he starts to hum along. This is further reinforced when she offers Sheldon his favorite drink, Strawberry Quik. She also prepared "spaghetti with little pieces of hot dog cut up" for dinner, which is Sheldon's favorite since his mother used to make it for him. Sheldon is thrilled, and says they should do this more often – instantly realizing he’s been caught in Amy's "trap" as Amy stands next to him with a big smile. At the end of the episode, they were playing doctor "Star Trek style" (Amy dressed in Star Trek attire). Amy’s actions seem to work on Sheldon, who isn’t happy about it but makes no attempt to stop her.

<p style="margin-top:0.4em;margin-bottom:0.5em;line-height:19.200000762939453px;font-family:sans-serif;">In the final fifth season episode "The Countdown Reflection", Sheldon takes Amy's hand as Howard is launched into space. Amy glances over at him looking quite surprised.

[edit] Religion
<p style="line-height:19.200000762939453px;font-family:sans-serif;">Religion plays a minor role in the series. Sheldon was raised in a fundamentalist Christian household. He refers to his childhood as "hell" during his date in "The Robotic Manipulation", and a recurrent theme is his conflict with his devout mother, Mary, whose creationist beliefs often clash with Sheldon's understanding of evolution. In "The Lunar Excitation", Sheldon mentions his promise to Mary to attend church once a year. In "The Wheaton Recurrence", after scoring a spare in bowling, Sheldon happily exclaims "Thank you, Jesus! ...as m

<p style="line-height:19.200000762939453px;font-family:sans-serif;">y mother would say." In the episode "The Zarnecki Incursion", Sheldon can be heard exclaiming

<p style="font-family:sans-serif;"> "Why hast thou forsaken me, o deity whose existence I doubt?" According to Raj, when Sheldon got food poisoning at the Rose Bowl, he begged the deity in which he didn't believe to kill him quickly. Sheldon often uses "Lord" as an interjection.

<p style="margin-top:0.4em;margin-bottom:0.5em;line-height:19.200000762939453px;font-family:sans-serif;">Howard is Jewish and Raj is of the Hindu faith, both semi-observant, apparently defying many religious customs without worry. They frequently flout dietary prohibitions and tend to give each other grief about them — In the episode "The Spaghetti Catalyst," Raj quotes from the book of Leviticus after Howard eats pork, and Howard counters with the fact that he keeps quiet when Raj eats a Whopper. Still, Raj mentions reincarnation and explains his belief in karma, stating that he believes it to be "practicallyNewtonian – for every action there is an equal and opposite reaction." Howard celebrates at least some Jewish holidays, refuses to pray to another god so he doesn't "burst into flames", and refuses to get tattoos so he "can be buried in a Jewish cemetery".

<p style="margin-top:0.4em;margin-bottom:0.5em;line-height:19.200000762939453px;font-family:sans-serif;">Neither Leonard's nor Penny's religious convictions are made clear. Leonard approaches Christianity with less skepticism than Sheldon.<sup class="noprint Inline-Template" style="line-height:1em;white-space:nowrap;">[episode needed] Penny has expressed belief in ghosts, astrology, psychics and voodoo. Bernadette is Catholic, and is frequently seen wearing a necklace with a cross, while Amy is agnostic, stating in "The Lunar Excitation" that she understands the notion of a deity but is baffled by the notion of one that takes attendance.

[edit] Howard's mother
<p style="line-height:19.200000762939453px;font-family:sans-serif;">In many episodes, Howard has shouting conversations with his overprotective mother (voiced by Carol Ann Susi). She is dependent on Howard, as he is on her. She speaks with aBrooklyn-esque accent, though she comes from New Jersey. Other characters frequently do impressions of her, and Bernadette's rendition is especially accurate. She always interacts with the cast from another room or on the telephone. She has never been seen, though she did appear momentarily in the overhead photo of Howard and Bernadette's wedding. But still, her face was never shown.