The Big Bang Theory is centered on five characters living in Pasadena, California: roommates Leonard Hofstadter and Sheldon Cooper; Penny, a waitress and aspiring actress who lives across the hall; and Leonard and Sheldon’s equally geeky and socially awkward friends and co-workers, mechanical engineer Howard Wolowitz and astrophysicist Raj Koothrappali. The geekiness and intellect of the four guys is contrasted for comic effect with Penny’s social skills and common sense.
Season 1 | Episode 1 Brilliant physicist roommates Leonard and Sheldon meet their new neighbor Penny, who begins showing them that as much as they know about science, they know little about actual living.
Season 1 | Episode 2 Leonard volunteers to sign for a package in an attempt to make a good impression on Penny, but when he enlists Sheldon for help, his attempt at chivalry goes terribly awry.
Season 1 | Episode 3 Leonard asks a woman out after he finds out that Penny is seeing someone.
Season 1 | Episode 4 Sheldon's getting fired forces him to explore what life has to offer outside physics, leaving Leonard to take drastic action to snap his friend out of his funk.
Season 1 | Episode 5 Fearing he's wasting his time on Penny, Leonard ends up making a connection with Leslie.
Season 1 | Episode 6 Penny hosts a Halloween party, putting Leonard, Sheldon, Wolowitz, and Koothrappali through a new test of their social skills.
Season 1 | Episode 7 With Wolowitz AWOL with one of her friends, Penny's recruited to fill in for him on the guys' Halo team
Season 1 | Episode 8 Raj's parents set him up on a blind date, but just when he discovers he can talk to her, she shows interest in Sheldon.
Season 1 | Episode 9 When they're invited to present at a physics conference, Sheldon's reluctance to share the credit leads to a tiff between him and Leonard, and Penny's intervention only exacerbates the situation.
Season 1 | Episode 10 Leonard and Sheldon each lie to avoid seeing Penny's concert, but Sheldon's is a bit too complicated for his own good.
Season 1 | Episode 11 With his friends knowing how sour he acts when sick—and avoiding him as a result—Sheldon is nursed by Penny, who hasn't a clue what she's in for.
Season 1 | Episode 12 With Sheldon rattled over meeting Dennis, a 15-year-old physicist who's smarter than he, Leonard helps him look for a way to debunk Dennis's research.
Season 1 | Episode 13 Sheldon finds himself booted from the gang's Physics Bowl team and replaced with Leslie, so he forms his own team, hoping to prove he's superior.
Season 1 | Episode 14 When delivery of another collectible leads to Penny's lashing out at Leonard, he decides it's time to give up his habit, much to his friends' protestation.
Season 1 | Episode 15 The rest of the gang fall for Sheldon's twin sister, and Leonard's plan to win her heart is derailed when Sheldon declares he'll be the one to decide who can date her.
Season 1 | Episode 16 Penny wants to throw a surprise party for Leonard, but Sheldon's indulgence at an electronics store throws her off-track.
Season 1 | Episode 17 Penny's break-up spurs Leonard to summon the courage to ask her out, and each goes to Sheldon for advice on their upcoming date.
Season 10 | Episode 1 After Sheldon’s mother and Leonard's father share an evening together, everyone deals with an awkward morning the next day. Also, Penny’s family arrives for the wedding ceremony, including her anxiety-ridden mother, Susan, and her drug dealing brother, Randall.
Season 10 | Episode 2 Colonel Williams, an Air Force representative from the Department of Material Command sits down to talk with Wolowitz.
Season 10 | Episode 3 Tensions rise when the boys struggle to complete their government project on time and Sheldon tries an energy drink to stay awake. Also, Penny and Amy go to a “party” at Bert the geologist’s house, and Koothrappali learns Bernadette’s true feelings about her pregnancy when they clean out the future baby room.
Season 10 | Episode 4 When Amy’s apartment floods, she proposes a “cohabitation experiment” with Sheldon. Also, Howard and Bernadette are upset when Koothrappali learns the gender of the baby before they do.
Season 10 | Episode 5 Leonard and Penny must separate a quarreling Sheldon and Amy when their cohabitation does not go as planned, and Sheldon threatens to break off their relationship when Amy refuses to adhere to the bathroom schedule. Also, Howard and Bernadette find unexpected guests at their house when they decide to stay home from a planned vacation.
Season 10 | Episode 6 Penny is surprised to learn she has fans of her performance in "Serial Ape-ist" when she attends Van Nuys Comic Con with Leonard. Also, Amy hosts a Sheldon-style brunch at Penny’s apartment, and Wolowitz makes an impulsive purchase when he starts stressing out about the baby on the way.
Season 10 | Episode 7 In order to continue living with Sheldon, Amy lies to him about repairs being made to her apartment and they host an "on location" episode of "Fun With Flags" in Penny’s apartment. Also, Leonard lets Penny decorate Sheldon’s old room after he learns that she has been secretly moving Leonard’s collectibles into storage.
Season 10 | Episode 8 After a successful experiment combining their genes, Sheldon will stop at nothing to convince Amy they should procreate. Also, Koothrappali is embarrassed to tell the gang what the new woman he’s dating does for a living.
Season 10 | Episode 9 When Bert, a Caltech geologist, wins the MacArthur Genius fellowship, Sheldon is overcome with jealousy. Also, Wolowitz finds an old remote control Stephen Hawking action figure he invented.
Season 10 | Episode 10 Sheldon and Leonard try to divvy up their shared belongings, but can’t agree on anything. Also, Koothrappali and Stuart fight to be the most helpful during Bernadette’s final weeks of pregnancy.
Season 10 | Episode 11 Howard and Bernadette welcome their new baby and Sheldon and Amy celebrate Amy’s birthday.
Season 10 | Episode 12 Sheldon and Amy visit Leonard and Penny for the first time since the holidays and share details about their terrible trip to Texas.
Season 10 | Episode 13 When Penny feels that Leonard is taking her for granted, she decides to go on a spa weekend with Amy. Also, Wolowitz and Koothrappali try to fix a squeaky floorboard in the baby’s room.
Season 10 | Episode 14 Sheldon beta-tests an MIT invention after hearing it can help him read people’s emotions. Also, Leonard can’t hide his feelings when Penny announces her brother is coming to town, and Raj invites his ex-girlfriends over to give him dating advice.
Season 10 | Episode 15 Leonard and Wolowitz try to distract Sheldon when he slows the progress of their guidance system. Also, Penny and Amy take Bernadette out for the night, leaving Raj and Stuart to care for baby Halley.
Season 10 | Episode 16 Sheldon and Amy have their first fight since moving in together, and Koothrappali is shocked at the realities of financial independence when he stops receiving support from his father.
Season 10 | Episode 17 With Koothrappali cut off from his father’s fortune, he appoints Sheldon to help him get out of debt. Also, Penny considers joining Leonard at Comic-Con.
Season 10 | Episode 18 When Raj moves out of his apartment, Leonard and Penny offer him Sheldon's old room.
Season 10 | Episode 19 Leonard, Penny and Raj adjust to their new living arrangement, and Sheldon takes an interest in Amy’s work.
Season 10 | Episode 20 Sheldon pushes himself to the limit when he collaborates on projects with Leonard and Wolowitz as well as Amy on the same day. Also, Bernadette is nearing the end of her maternity leave and must return to work.
Season 10 | Episode 21 Howard and Bernadette have a hard time leaving Halley in day care when Bernadette returns to work. Also, Bert introduces the gang to his new girlfriend, Rebecca.
Season 10 | Episode 22 Leonard isn’t thrilled when Penny considers taking a new job offered by her ex-boyfriend, Zack.
Season 10 | Episode 23 After Leonard, Sheldon and Wolowitz celebrate the completion of the top secret air force project, they are met with an unpleasant surprise. Also, Amy is offered a summer position as a visiting researcher.
Season 10 | Episode 24 The gang is concerned when Sheldon’s former admirer, Dr. Ramona Nowitzki, resurfaces while Amy is away at Princeton.
Season 11 | Episode 1 In the eleventh season opener, Amy gives Sheldon an answer to his proposal while Howard and Bernadette struggle with some unexpected news.
Season 11 | Episode 2 Leonard angers the university – and the entire physics community – after he gives an embarrassing interview. Also, Amy and Bernadette bond over having to hide their success from Sheldon and Howard.
Season 11 | Episode 3 Sheldon struggles with picking a wedding date. Amy decides she wants a wedding near a cliff which Sheldon doesn't want. Meanwhile Raj and Stuart fight over one of Bernadette's co-workers.
Season 11 | Episode 4 As Howard worries about fatherhood, he and Sheldon bond when they jointly assemble a model rocket. Meanwhile, Penny bonds with Leonard's mother, Beverly, much to his concern.
Season 11 | Episode 5 Sheldon and Koothrappali confide in Bernadette when they can't handle Amy and Wolowitz working together. Also, Penny and Leonard learn new tactics for how to deal Sheldon from an unlikely source.
Season 11 | Episode 6 Sheldon goes head-to-head with Wil Wheaton for the role of the new Professor Proton. Also, Penny steps in to take care of Halley when Bernadette and Wolowitz both wind up on bed rest.
Season 11 | Episode 7 Sheldon and Bert collaborate on a research project, despite Sheldon’s embarrassment. Also, Penny and Bernadette coach Koothrappali on how to navigate his relationship with Ruchi.
Season 11 | Episode 8 Leonard and Wolowitz are furious after they learn Sheldon went to work with the military behind their backs. Also, while Bernadette is on bed rest, she asks Raj to do some digging when she suspects Ruchi is trying to steal her job.
Season 11 | Episode 9 Sheldon tries to teach the guys a lesson after they cut him out of a potentially valuable Bitcoin investment. Also, a seven-year-old video reveals a secret about Leonard and Penny's relationship.
Season 11 | Episode 10 Sheldon and Amy try to eliminate stress from wedding planning by applying math to the process. Also, Koothrappali “breaks up” with Wolowitz after realizing his best friend is actually hurting his confidence.
Season 11 | Episode 11 Sheldon and Wolowitz plan birthday celebrations for Amy and Halley, respectively. Also, Leonard get a Christmas letter from his brother that causes him to spiral out about his own lack of accomplishments.
Season 11 | Episode 12 Sheldon and Amy will try to use science to see who should be their Maid of Honor and Best Man.
Season 11 | Episode 13 When Sheldon kicks Amy out to work solo, she and Leonard bond during a series of science experiments. Also, Bert the geologist replaces Wolowitz in the band Footprints on the Moon, and Sheldon finds Penny a surprising source of scientific inspiration.
Season 11 | Episode 14 Koothrappali finds himself in the middle of domestic drama when he learns the woman he's dating, has a very upset husband. Also, when Sheldon rents his old room back for a quiet place to work, he drives Leonard crazy by being a model tenant.
Season 11 | Episode 15 Leonard's book raises questions, and Amy guest stars on the new Professor Proton show.
Season 11 | Episode 16 When Bernadette won't go into labor, the gang tries different tactics to get things started. Howard confronts Bernadette after Amy accidentally reveals she's already chosen their son's name.
Season 11 | Episode 17 Leonard jumps through hoops to help secure the perfect wedding venue for Sheldon and Amy. Also, Bernadette and Wolowitz have a hard time deciding who should stay at home with the kids and who should go back to work.
Season 11 | Episode 18 Bill Gates visits Penny's work, and the gang schemes to meet him. Hilarity ensues.
Season 11 | Episode 19 When Leonard learns Sheldon is the president of the tenants association, he decides to run against him. Also, Bernadette encourages Wolowitz and Koothrappali to find the owner of a drone after they find it in the backyard.
Season 11 | Episode 20 A brilliant but reclusive scientist, Doctor Wolcott, invites Sheldon to his cabin in the middle of nowhere, and Leonard, Raj and Howard go along for the trip. Also, Penny and Bernadette improvise after Amy doesn’t like the tame bachelorette party they planned for her.
Season 11 | Episode 21 Sheldon’s comic book store experiences changes when writer Neil Gaiman puts Stuart’s store on the map. Also, Koothrappali takes credit for Penny’s astronomical discovery, and friendships are threatened.
Season 11 | Episode 22 Sheldon goes to Vegas to win money for science. Also, Penny and Bernadette take Amy wedding dress shopping, but her terrible choice entangles them in a web of lies.
Season 11 | Episode 23 When Sheldon learns that his mother won’t attend his wedding unless he invites his brother, Georgie, he and Leonard travel to Texas to end a family feud. Also, the Wolowitz kids inadvertently infest Amy, Bernadette, Wolowitz and Koothrappali with pinkeye.
Season 11 | Episode 24 When Amy's parents and Sheldon's family arrive, everybody is focused to make sure all wedding arrangements go according to plan – everyone except the bride and groom.
Season 2 | Episode 1 Penny's first date with Leonard goes awry; Penny finds Sheldon to be an unwilling confidant.
Season 2 | Episode 2 A jealous Leonard reacts to Penny's new guy by rebounding with Leslie.
Season 2 | Episode 3 Sheldon creates a monster when he introduces Penny to online gaming.
Season 2 | Episode 4 Raj gets an inflated ego and makes a play for Penny after being referenced in a magazine article.
Season 2 | Episode 5 Leonard and his friends stage an intervention to force Sheldon to face his fear of driving.
Season 2 | Episode 6 Sheldon and the gang are confused when a young grad student is attracted to him.
Season 2 | Episode 7 When Sheldon bans Penny from the apartment for numerous minor infractions, she decides to retaliate.
Season 2 | Episode 8 Leonard inadvertently steals away the new woman Wolowitz thinks is the love of his life.
Season 2 | Episode 9 Sheldon is thrilled when Leonard starts dating a woman who meets Sheldon's stringent standards.
Season 2 | Episode 10 Leonard asks Penny for advice when his new relationship starts moving too fast.
Season 2 | Episode 11 Penny starts dating Leonard's handsome colleague; Leonard and his friends are tortured by Sheldon's obsession with gift-giving etiquette.
Season 2 | Episode 12 Penny's criticism of Wolowitz's romantic life pushes him into depression and AWOL for a fighting robot battle the rest of guys are depending on him for.
Season 2 | Episode 13 Sheldon creates a scientific procedure for making friends.
Season 2 | Episode 14 Sheldon's solution to Penny's financial difficulty leads to a confrontation between Leonard and Penny's ex-boyfriend.
Season 2 | Episode 15 Leonard and Penny are drawn together after a disastrous visit from Leonard's mother.
Season 2 | Episode 16 A paintball game leads to a fight between Sheldon and Penny, and romance for Leslie and Wolowitz.
Season 2 | Episode 17 Leonard, Sheldon and Wolowitz are ecstatic to learn that a famous science-fiction actress (Summer Glau) is on board the train they are taking to San Francisco.
Season 2 | Episode 18 Penny's home business turns into a complete nightmare when Sheldon takes over.
Season 2 | Episode 19 Penny squares off with a new beautiful female neighbor who may become the building's "new Penny."
Season 2 | Episode 20 A fellow comic book enthusiast's hitting on Penny leads to Leonard and Howard going to a bar's Ladies' Night.
Season 2 | Episode 21 Leonard and Koothrappali escort a heartbroken Wolowitz to Las Vegas, and Sheldon becomes locked out of his apartment and must stay with Penny.
Season 2 | Episode 22 Penny's second date with Stuart sees her making a comment that gives Leonard new hope for a relationship with her. Wolowitz realizes there's a crucial error in a NASA project he's working on.
Season 2 | Episode 23 The guys' plan to work over the summer at the North Pole makes Penny revaluate her feelings for Leonard.
Season 3 | Episode 1 When Sheldon learns the guys tampered with his expedition data he got from the arctic, he leaves to Texas in disgrace. This results in the guys following him, which threatens Leonard's hope for some romantic time with Penny and the guys' friendship with Sheldon.
Season 3 | Episode 2 Leonard and Penny struggle to recover from an awkward first hookup while Sheldon and Howard stake their best comic books on a bet to determine the species of a cricket.
Season 3 | Episode 3 Howard and Raj visit a Goth nightclub to pick up women while Sheldon attempts to build a better Penny using chocolate-based behavior modification.
Season 3 | Episode 4 Raj must find a new job or be sent back to India, but Sheldon has a solution, which leaves Leonard and Penny dealing with Howard as a third wheel.
Season 3 | Episode 5 After overhearing that Wil Wheaton is entering a trading-card competition, Sheldon decides to enter it himself. Meanwhile, Penny sets up one of her friends on a date with Wolowitz.
Season 3 | Episode 6 Sheldon becomes Leonard's teacher in order to understand football, while an incident with flying a kite threatens Howard and Raj's friendship.
Season 3 | Episode 7 A squabble between Leonard and Penny sees Sheldon playing mediator, though out of his own incovenience from the sitiation rather than altruism.
Season 3 | Episode 8 With Leonard, Howard and Raj away camping in the desert, an injured Penny has only Sheldon to rely on.
Season 3 | Episode 9 After he's humiliated on National Public Radio, Sheldon vows to destroy Kripke, while Wolowitz tries not to destroy his new relationship with Bernadette.
Season 3 | Episode 10 Penny gets help from Sheldon in order to understand what Leonard's work is, while Wolowitz develops a jealousy when Leonard starts hanging out with his new girlfriend.
Season 3 | Episode 11 A Christmas visit from his mother has Leonard discovering she's kept a lot of news from him that she shares with Sheldon and worrying if she'll approve of his romance with Penny.
Season 3 | Episode 12 Leonard is aghast to find out a secret of Penny's: she believes in psychics. Meanwhile, Sheldon tries to assist Koothrappali in picking up a girl at a university mixer.
Season 3 | Episode 13 When their apartment is robbed, Leonard and Sheldon turn to their friends to create a state-of-the-art security system.
Season 3 | Episode 14 Sheldon's search for the answer to a physics problem leads him to work at the Cheesecake Factory with Penny.
Season 3 | Episode 15 Leonard can only bring one guest on a trip to see CERN's Large Hadron Collider (the world's largest and highest energy particle accelerator) in Switzerland on Valentine's Day.
Season 3 | Episode 16 Sheldon winds up in traffic court when he gets a ticket because of Penny.
Season 3 | Episode 17 When the guys find a ring from "The Lord of the Rings" at a garage sale, it threatens to tear them apart.
Season 3 | Episode 18 Sheldon's friends come to his aid when his fear of public speaking stands between him and a coveted award.
Season 3 | Episode 19 A fight between Leonard and Penny threatens their relationship, while Sheldon battles Wil Wheaton in bowling.
Season 3 | Episode 20 When Leonard and Penny aren't speaking, Sheldon goes to extremes to keep them both happy.
Season 3 | Episode 21 Leonard and Sheldon compete for the attention of a famous female physicist.
Season 3 | Episode 22 Leonard tells Penny about how he met Sheldon for the first time...and what happened to the elevator.
Season 3 | Episode 23 While Penny worries that dating Leonard has ruined her for normal guys, Wolowitz and Koothrappali search for Sheldon's perfect match online.
Season 4 | Episode 1 Penny tags along on Sheldon's first ever date; Wolowitz finds a new use for a robotic arm.
Season 4 | Episode 2 Realizing he will not live long enough to download his consciousness into a robot body, Sheldon tries to extend his life span.
Season 4 | Episode 3 The guys are concerned as Sheldon searches for an alternative to human companionship.
Season 4 | Episode 4 An embarrassing secret of Wolowitz's comes to light, while Sheldon and Raj have a small war at work.
Season 4 | Episode 5 Leonard realizes he’s the only one without a girlfriend, while Sheldon wants to get rid of his.
Season 4 | Episode 6 Leonard keeps an affair a secret from Sheldon, Howard and Raj.
Season 4 | Episode 7 Sheldon's answers during an FBI interview put Wolowitz's security clearance in jeopardy.
Season 4 | Episode 8 While the guys camp in line for a long-awaited movie screening, Penny and Bernadette invite Amy to her first slumber party.
Season 4 | Episode 9 Penny asks Leonard to lie to her father, while Howard, Raj and Bernadette pull an all-nighter at a telescope.
Season 4 | Episode 10 Amy finds she has sexual feelings for Penny's ex, while Koothrappali and Wolowitz try to prove who would be the better superhero.
Season 4 | Episode 11 The guys find a "super" use for Penny's new boyfriend, Zack, when they enter a costume contest as the Justice League.
Season 4 | Episode 12 Leonard's idea for a smartphone app derails his friendship with Sheldon.
Season 4 | Episode 13 Bernadette runs into her ex-boyfriend while attending a science event with Wolowitz.
Season 4 | Episode 14 Hoping it will make him a better teacher, Sheldon has Penny give him acting lessons. Raj has fantasies about a friend's girlfriend.
Season 4 | Episode 15 A wealthy donor to the university makes Leonard consider how far he's willing to go for the sake of science.
Season 4 | Episode 16 As Wolowitz contemplates taking things with Bernadette to the next level, Leonard rekindles his relationship with Raj's sister.
Season 4 | Episode 17 Sheldon becomes concerned when everybody begins to hang out at Raj's apartment and discovers Leonard is the center of the group.
Season 4 | Episode 18 Sheldon is baffled by Wolowitz's magic trick. Meanwhile, Leonard realizes dating Priya may make it impossible to continue being friends with Penny.
Season 4 | Episode 19 Sheldon's online-game account is hacked by Todd Zarnecki, who then proceeds to steal all his items prompting the guys to go on a quest to retrieve them. Penny, Bernadette and Amy discuss how Penny groomed Leonard to be willing to try various things and more adventurous boyfriend... for some other woman — Priya.
Season 4 | Episode 20 Sheldon and Amy decide to start several rumors about the others as a test. Meanwhile, Howard takes his relationship with Bernadette to even higher level.
Season 4 | Episode 21 When Leonard spends too much time in the shower with Priya, Sheldon charges Leonard with two violations of the roommate agreement. However, before he can get too far, Priya uses her skills as a lawyer to nullify the charges due to the agreement's vague wording, much to Sheldon's dismay. When the guys take advantage of Priya's skills in order to eat Greek food on pizza night, Sheldon goes to Penny, who invites him to a girls' night out with Amy and Bernadette, which Sheldon agrees to after Penny mentions that they may be talking trash about Priya. After the girls drink some cocktails, they decide to take Sheldon dancing, which Sheldon reluctantly goes along with. After dancing, Sheldon takes an intoxicated Amy back to her apartment and as well as talking about Priya, meets a monkey who is addicted to smoking cigarettes. Amy tells Sheldon not to give in to Priya's law skills, before kissing him and going to her bathroom to vomit.
Season 4 | Episode 22 Raj attempts to cure his social anxiety disorder while Penny uses Bernadette to spy on Leonard and his girlfriend.
Season 4 | Episode 23 When Howard finally breaks the news to his mom that he's engaged to Bernadette, it lands her in the hospital.
Season 4 | Episode 24 When Bernadette receives her PhD, Wolowitz feels emasculated. Raj and Leonard swap places and Penny does something she's regrets.
Season 5 | Episode 1 Penny is worried with how damaged her friendship with the guys will be in the aftermath of her sleeping with Raj while Sheldon becomes the leader of the paintball team.
Season 5 | Episode 2 A fight between Sheldon and Penny leaves Amy caught in the middle, while Leonard tries to spice up his long-distance relationship with Priya.
Season 5 | Episode 3 Leonard and Amy get to know each other better, while Howard and Bernadette spend the weekend with Mrs. Wolowitz.
Season 5 | Episode 4 Penny plays Matchmaker for Raj, which results in him finding a girl he is comfortable talking to.
Season 5 | Episode 5 Sheldon and Leonard get invited to a party at Wil Wheaton's house, and Howard gets an out-of-this-world opportunity.
Season 5 | Episode 6 Sheldon's mother, Mary Cooper, comes to visit, but Sheldon is annoyed that she also spends time with the rest of the gang, instead of catering to his every demand.
Season 5 | Episode 7 A cute comic book artist puts Leonard and Priya’s relationship to the test, while Sheldon tries to scare the guys for Halloween.
Season 5 | Episode 8 Amy becomes heartbroken when she discovers that Penny and Bernadette went wedding dress shopping without her.
Season 5 | Episode 9 Leonard and Penny try hanging out as friends on a 'non-date', but end up purposely ruining each others chances with perspective dates. Meanwhile, Sheldon enlists the help of Bernadette and Amy to overcome his fear of birds.
Season 5 | Episode 10 When Stuart asks Amy out on a date, Sheldon must confront his feelings and consider where his relationship with Amy is going.
Season 5 | Episode 11 Leonard must face his fears after being contacted by his high school tormentor.
Season 5 | Episode 12 Sheldon gets in trouble with Amy when he isn't impressed by her recent accomplishment, and Howard must come to grips with Bernadette's dislike of children.
Season 5 | Episode 13 Leonard, who broke up with Priya, asks Penny out to a spur-of the-moment romantic dinner for two, and the duo contemplates on their relationship.
Season 5 | Episode 14 Leonard and Penny deal with the idea of starting a relationship again and Raj finally finds a "woman" he can talk to without being drunk, in the form of Siri on his new phone. Meanwhile, Sheldon decides to start a YouTube series entitled "Sheldon Cooper presents Fun with Flags" with the help of Amy.
Season 5 | Episode 15 Sheldon's selfish demands force Leonard to reconsider their friendship. Meanwhile, Wolowitz tries to pick his astronaut nickname.
Season 5 | Episode 16 When Sheldon is forced to take his vacation, he goes to work with Amy in her neurobiology lab.
Season 5 | Episode 17 Penny is horrified when Amy gives her a gift: a huge, quite horrible painting of the two of them. With no good way to avoid displaying it, she only hangs it up when Amy is over. When Amy catches her taking the painting down, she's embarrassed and angry until Penny lies and says the gift made Bernadette jealous. When the deranged Professor Rothman is forced to retire, both Sheldon and Kripke vie for his office. President Siebert refuses to resolve the dispute, so Leonard arranges a one-on-one basketball game to decide (since they're both equally bad at sports). Neither one can even make a single basket, so they end up deciding by seeing who can bounce the ball the highest. Sheldon wins; unfortunately, the office is not what he'd hoped for: the thermostat is located in the office of a professor going through the hot flashes of menopause (thus Sheldon is too cold), the mockingbird outside his window is off-key with the annoying windchimes, the perpetually naked Professor Rothman refuses to vacate, and the Geology Department upstairs makes too much noise. Finally, Sheldon gets his head stuck in the wall in an existing hole, after which Leonard takes his picture before he goes for help.
Season 5 | Episode 18 Sheldon becomes agitated when his regular barber is out sick. Astronaut training causes Howard to reconsider wanting to go into space. Penny beats Leonard in chess, the first time she plays.
Season 5 | Episode 19 Sheldon must choose between joining Amy at her aunt's birthday party or playing videogames all weekend with the guys.
Season 5 | Episode 20 Penny buys Leonard and Sheldon “Star Trek” collectibles as a thank-you, leading Sheldon to be haunted by Mr. Spock. Meanwhile, Raj decides he has met the “Future Mrs. Koothrappali” after his parents set him up on a date.
Season 5 | Episode 21 When Wolowitz gets to work with Stephen Hawking, Sheldon is willing to do anything to meet his hero.
Season 5 | Episode 22 After the guys throw Howard a bachelor party, Bernadette reconsiders marrying him after learning about his sexual history.
Season 5 | Episode 23 When NASA moves up Howard's mission, he must face his fears and Bernadette's dad, thus putting the wedding plans in jeopardy. Meanwhile, Leonard says something surprising to Penny in the bedroom.
Season 5 | Episode 24 The fifth season ends with Howard and Bernadette deciding to get married before his NASA mission, causing the gang to scurry into overdrive in an effort to stage the wedding. NASA astronaut Mike Massimino has a cameo as himself.
Season 6 | Episode 1 With his friends on dates, Raj must face his loneliness. Also, Wolowitz is caught in an argument between Bernadette and his mom, even while he’s in space
Season 6 | Episode 2 When Sheldon learns that Penny is thinking about breaking up with Leonard, he tries to intervene. Meanwhile, in space, the other astronauts pick on Howard.
Season 6 | Episode 3 Amy feels threatened when Sheldon hires a young female assistant, and the pressure of being in space takes its toll on Wolowitz.
Season 6 | Episode 4 When Wolowitz returns from space, he doesn’t get the hero’s welcome he expected. Meanwhile, Game Night turns into a battle of the sexes.
Season 6 | Episode 5 The gang celebrates Halloween at Stuart’s comic book store. Meanwhile, Leonard seduces Penny with science.
Season 6 | Episode 6 Sheldon’s relationship with Stephen Hawking is threatened over a game of “Words with Friends,” and Penny secretly enrolls in a class at the local college.
Season 6 | Episode 7 Wolowitz struggles with moving out of his mother’s house. Meanwhile, Sheldon is caught in the middle of an argument between Amy and Wil Wheaton.
Season 6 | Episode 8 Raj and Howard try to to figure out why Sheldon disappears at 2:45 every afternoon; jealousy arises in Penny and Leonard's relationship.
Season 6 | Episode 9 When the University reassigns Sheldon’s parking spot to Wolowitz, their fight affects the whole gang.
Season 6 | Episode 10 When Amy gets sick, Sheldon tries to nurse her back to health; Wolowitz and his father-in-law plan a fishing trip.
Season 6 | Episode 11 During a game, Sheldon revisits Christmas memories; Amy, Penny and Bernadette look for a date for Koothrappali.
Season 6 | Episode 12 When Sheldon is accused of sexual harassment, he ends up getting Raj, Leonard and Wolowitz in trouble.
Season 6 | Episode 13 As the guys don costumes and go on a road trip to a comic book convention, the ladies decide to stay home and try to interpret a comic book.
Season 6 | Episode 14 Sheldon faces a crisis of confidence when he is forced to work with his nemesis, Barry Kripke; Raj and Howard buy expensive action figures of themselves.
Season 6 | Episode 15 A fight between Sheldon and Leonard impacts Amy and Penny's living arrangements; while Howard is away, Raj helps Mrs. Wolowitz out.
Season 6 | Episode 16 The guys search for a perfect Valentine's Day gift for their significant others; Stuart and Raj host a "lonely people" party at the comic book store.
Season 6 | Episode 17 After a bad date, Koothrappali decides to never leave his apartment; Penny's acting skills impress Sheldon.
Season 6 | Episode 18 Leonard, Sheldon and Wolowitz talk to junior high girls about science-related careers; Raj plans a date with Lucy.
Season 6 | Episode 19 Howard considers whether or not he should open a letter from his father; Penny and Leonard host a "grown-up" cocktail party.
Season 6 | Episode 20 The girls get involved when Leonard, Sheldon and Raj compete for tenure at the University.
Season 6 | Episode 21 Amy tries to help Sheldon get over his compulsive need for closure when one of his favorite TV shows is canceled; Raj discovers a secret about Lucy.
Season 6 | Episode 22 Leonard and Sheldon hire the host (Bob Newhart) of their favorite childhood TV show to perform; Bernadette and Howard run into trouble while dog-sitting for Raj's pet.
Season 6 | Episode 23 Amy and Sheldon's relationship takes a surprising turn during a game of "Dungeons & Dragons"; Lucy and Koothrappali have an awkward date.
Season 6 | Episode 24 When Leonard receives an exciting opportunity to work overseas, Penny and Sheldon are thrown for a loop.
Season 7 | Episode 1 With Leonard away, Sheldon and Penny spend quality time together sharing intimate secrets. Also, Wolowitz helps Raj get over his ex-girlfriend.
Season 7 | Episode 2 Leonard and Sheldon's friendship is tested; Wolowitz's relationship with his mom causes a threat to his masculinity.
Season 7 | Episode 3 When the entire gang competes in a scavenger hunt designed by Raj, it brings out the best - and worst - in everyone.
Season 7 | Episode 4 Beverly Hofstadter writes a psychology book about Leonard which Penny buys and reads. Sheldon wants to ruin something for Amy after she ruins an Indiana Jones movie for him. Raj and Stuart try online dating.
Season 7 | Episode 5 Amy starts working at Caltech which causes friction with Sheldon. Howard agrees with Sheldon who mentions this to Bernadette causing a big fight for the Wolowitzes.
Season 7 | Episode 6 Sheldon's latest scientific breakthrough leaves him feeling like a fraud; a romantic gesture between Howard and Bernadette causes Penny to up her game with Leonard.
Season 7 | Episode 7 When Professor Proton asks Leonard for help with an experiment, Sheldon retaliates by befriending Proton's rival, Bill Nye.
Season 7 | Episode 8 When a mistake comes to light, Sheldon makes Leonard walk a mile in his shoes; Penny decides to confront Raj's ex.
Season 7 | Episode 9 Sheldon protests when the gang drags him to Mrs. Wolowitz’s house for Thanksgiving. Meanwhile, Penny and Leonard must deal with a mistake from her past.
Season 7 | Episode 10 Leonard and Amy help Sheldon cope with the shame he’s feeling after his accidental contribution to science is disproved. Meanwhile, Raj must stay with Howard and Bernadette for a week.
Season 7 | Episode 11 While Sheldon is in Texas, the rest of the gang realizes how much he has changed their lives as they decorate the apartment Christmas tree.
Season 7 | Episode 12 When Penny’s big acting break on NCIS is a bust, Leonard struggles to help her, which results in Penny asking Leonard a bold relationship question. Meanwhile, Sheldon tries to learn how to be funny and Raj tries to work on his “game” before talking to girls.
Season 7 | Episode 13 Sheldon tries to relax after he is forced to take a vacation. Meanwhile, Leonard struggles to be supportive of Penny after she quits her job, and Bernadette seeks Stuart’s help in replacing one of Howard’s comic books.
Season 7 | Episode 14 After the guys can’t get Comic-Con tickets, Sheldon tries to hold his own convention and winds up spending a wild night with James Earl Jones. Meanwhile, the girls see if they can act like “grown-ups”.
Season 7 | Episode 15 Sheldon and Amy go on a trip to wine country with Howard and Bernadette; Penny and Leonard rush Raj's dog to the vet.
Season 7 | Episode 16 Leonard buys a dining room table and it causes Sheldon to reevaluate the changes in his life. Meanwhile, Wolowitz is offered a chance to go back to space and Bernadette struggles with whether or not to encourage him.
Season 7 | Episode 17 Bernadette tries to negotiate peace between Sheldon and Wolowitz; Penny receives an embarrassing offer; Raj wants Amy to write to a woman on his behalf.
Season 7 | Episode 18 When Sheldon visits his Mom in Houston, he is forced to confront a new reality. Meanwhile, Raj’s ‘Murder Mystery’ party starts some fights within the gang.
Season 7 | Episode 19 While Raj is wracked with guilt when he tries to date two women at once, Penny wrestles with whether to take a role in a cheesy movie and Sheldon is torn trying to choose between two gaming systems.
Season 7 | Episode 20 Sheldon faces a personal crisis after deciding he’s wasting his time with string theory. Meanwhile, a double date between Raj, Emily and the Wolowitzes ends in embarrassment for Howard.
Season 7 | Episode 21 To prepare for a date with Emily, Howard acclimates Raj to horror movies. Penny and Sheldon are upset when they discover Amy and Bernadette lied to avoid hanging out with them.
Season 7 | Episode 22 As the gang celebrates Star Wars Day, Sheldon discovers he is having difficulty dealing with the death of Professor Proton.
Season 7 | Episode 23 A bad day causes Penny to reevaluate her life choices – including Leonard. Meanwhile, Howard and Bernadette struggle to care for Mrs. Wolowitz, and Raj gets relationship advice from Sheldon.
Season 7 | Episode 24 Sheldon get upset about his career, the destruction of the comic book store and Leonard and Penny's future living arrangements. Howard and Bernadette can't keep hold of a carer for his mother. With his entire world changing around him, Sheldon considers a major move.
Season 8 | Episode 1 Leonard and Amy make an unexpected trip to Arizona to fetch Sheldon; Penny interviews for a job at Bernadette's company; Stuart's relationship with Mrs. Wolowitz disturbs Howard.
Season 8 | Episode 2 When Sheldon must teach a class, Howard decides to take it. Amy takes advantage of the tension between Penny and Bernadette.
Season 8 | Episode 3 Wolowitz feels nervous when he is asked to throw the first pitch at a Los Angeles Angels game. Penny and Leonard want to prove Sheldon wrong after he says he and Amy are the better couple.
Season 8 | Episode 4 Raj's honesty comes back to haunt him when his new girlfriend is unfriendly to Penny. The guys think about becoming part owners in Stuart's store.
Season 8 | Episode 5 During their weekend in Las Vegas, Bernadette and Amy accuse Penny of being a buzz kill. The guys try to invent the next big thing.
Season 8 | Episode 6 Sheldon and Raj test whether they could survive a dark-matter research expedition in a salt mine by simulating the conditions in a steam tunnel deep underground. Leonard and Penny seek advice from Howard and Bernadette after they fight about money.
Season 8 | Episode 7 The guys try to help Penny out of an awkward work dilemma, when a smitten doctor shows up at her door after her flirtatious sales techniques work a little too well. Meanwhile, Amy and Bernadette argue over whether or not female scientists should play up their sexuality.
Season 8 | Episode 8 When the gang recreates a high-school prom night on the roof of the guys'; apartment building, Sheldon feels pressure to participate in all the typical romantic traditions.
Season 8 | Episode 9 When Leonard gets minor surgery on his nose, Sheldon is the one in need of sympathy. Meanwhile, Raj's parents' impending divorce causes Howard and Bernadette to work on their own marriage.
Season 8 | Episode 10 While Sheldon says a tearful goodbye to the final installment of "Fun with Flags", Leonard, Howard and Raj search for something significant in a dead professor's research. And Bernadette is shocked to learn of her co-workers’ true feelings from Penny.
Season 8 | Episode 11 Leonard and Howard turn to Raj for help in dealing with a work emergency when they nearly come to blows after blaming each other for a potential disaster at the university. Amy throws an authentic Victorian Christmas party, while Sheldon seeks revenge on her for making him celebrate the holidays.
Season 8 | Episode 12 Wolowitz tries to distract Raj, who is anxiously awaiting data from a space probe he helped launch. Meanwhile, Sheldon and Leonard go dress shopping with Penny and Amy.
Season 8 | Episode 13 The gang tries to help Sheldon when he becomes stuck in a rut at work by increasing his anxiety level. Howard teases Raj with a new game called "Cinnamon or Emily?"
Season 8 | Episode 14 Leonard and Sheldon publish a paper which is widely accepted except for comments from an internet troll. Meanwhile, the girls reminisce about embarrassing incidents from their past.
Season 8 | Episode 15 Wolowitz receives some shocking news as everyone prepares for the reopening of Stuart’s comic book store. Penny teaches Sheldon how to “let it go,” but can’t follow her own advice after she learns something infuriating about Amy. Also, Leonard and Raj think they spot Nathan Fillion at a restaurant.
Season 8 | Episode 16 As a joke, Sheldon and Penny try an experiment designed to make participants fall in love. Also, Leonard, Amy, Raj and Emily spend the evening trying to escape a room with a “zombie.” And, after returning from Mrs. Wolowitz’ funeral, Bernadette and Howard run into trouble at the airport.
Season 8 | Episode 17 Trouble arises when Amy learns Sheldon has applied for a one-way mission to colonize Mars. Also, a trip to the pet store ends in a fight for Sheldon and Amy, Leonard surprises Penny with a very “adult” purchase, and Raj is caught snooping in Emily’s apartment.
Season 8 | Episode 18 Friction ensues when a magazine fails to mention Leonard in an article about the paper he co-wrote with Sheldon. Also, a blackout at Mrs. Wolowitz’s home leads to a final family dinner in her honor.
Season 8 | Episode 19 When Leonard and Sheldon are invited to speak at UC Berkeley, they take a detour to try to meet an idol. Also, when Bernadette and Howard battle over the fate of his Doctor Who TARDIS, Raj and Amy offer to settle the dispute with a game of ping pong.
Season 8 | Episode 20 When Sheldon and Amy build a blanket fort, they come to major crossroads in their relationship. Also, Wolowitz meets the half-brother he never knew he had, and when Penny is invited to appear on Wil Wheaton’s podcast, she and Leonard have a huge, on-air argument.
Season 8 | Episode 21 When Raj is asked to create a message in case a NASA mission discovers alien life, the guys fight over what he should do. Also, Penny is torn between auditioning for a movie or keeping her successful pharmaceutical sales job.
Season 8 | Episode 22 Wolowitz questions his engineering abilities when he and Sheldon can’t get a toy drone to fly. Meanwhile, a cancelled flight nearly prevents Leonard from giving the commencement address at his former high school, and Raj pits his parents against each other when his father cuts him off financially.
Season 8 | Episode 23 Personalities collide when Sheldon and Leonard’s mothers finally meet. Meanwhile, Howard finally decides to “man up” and do his fair share of the housework – but not without a little help from his friends.
Season 8 | Episode 24 Sheldon pushes Leonard and Penny to choose a date for their wedding and deals with dramatic changes in his own relationship with Amy.
Season 9 | Episode 1 After driving to Vegas to get married, Penny struggles with Leonard’s confession that he kissed another girl. Also, Sheldon doesn't know how to act after Amy pushes pause on their relationship.
Season 9 | Episode 2 Leonard confronts the woman he kissed on the North Sea in an attempt to set Penny's mind at ease. Also, Sheldon films a special episode of "Fun with Flags" after his breakup with Amy, and Bernadette feels guilty about withholding a secret from Penny.
Season 9 | Episode 3 The guys' science skills are put to the test when they get a flat tire during Leonard's bachelor party weekend in Mexico. Also, the girls force Penny to finally tell her family that she eloped with Leonard.
Season 9 | Episode 4 Sheldon learns of an impending change in his living arrangements and decides to revert back to 2003, a simpler time before he met Leonard and Penny. Also, Howard and Raj form a band to play at the Comic Book Store.
Season 9 | Episode 5 The guys take a fencing lesson from Barry Kripke and Sheldon finds himself in an awkward position when Kripke expresses interest in Amy. Also, when Stuart struggles to get female customers at the Comic Book Store, Penny, Amy and Bernadette come by to help him out.
Season 9 | Episode 6 In the midst of a nation-wide helium shortage, Sheldon and Leonard take desperate measures to get the supplies they need. Also, Penny and Bernadette download a dating app on Amy's phone to try and find her a new man.
Season 9 | Episode 7 Wil Wheaton interviews Sheldon for a Star Trek documentary where he reveals the ring and his plan to propose to Amy. Bernadette wants to start renovating the house and the topic of starting a family together with Howard is brought up.
Season 9 | Episode 8 Sheldon, Wolowitz and Koothrappali post an online advertisement to find Sheldon a new girlfriend. Also, when Amy is coy with details about a guy she is dating, Penny and Bernadette decide to spy
Season 9 | Episode 9 Sheldon and Amy try hanging out as friends when they spend Thanksgiving together at the aquarium. Also, Wolowitz reluctantly agrees to volunteer at the soup kitchen with Bernadette, Raj and Emily, and Penny discovers that Leonard knows more about her than she thought.
Season 9 | Episode 10 Sheldon has a revelation when he realizes why a song was stuck in his head. Also, Amy invites Dave over for dinner despite their previously awkward date, and Wolowitz and Koothrappali become obsessed with a fan of their band, "Footprints on the Moon".
Season 9 | Episode 11 After more than five years of dating, Sheldon and Amy spend their first night together. Also, Leonard, Wolowitz, and Koothrappali must decide who will take their extra Star Wars movie ticket.
Season 9 | Episode 12 Penny gets more than she bargained for when Leonard agrees to meet with a psychiatrist on her behalf. Also, Sheldon and Koothrappali collaborate on an astronomical discovery, and Wolowitz and Bernadette can't believe what they are feeling after Stuart moves out.
Season 9 | Episode 13 After having to deal with a sick Sheldon, Leonard, Penny and the gang try to treat themselves to a Sheldon-free weekend.
Season 9 | Episode 14 Meemaw meets Amy, but it isn't all roses. Meemaw seems to have an axe to grind with her. Sheldon comes to Amy's defense, but not before Meemaw lets a little secret of his slip.
Season 9 | Episode 15 Sheldon and Amy host a live Valentine's Day episode of Fun with Flags, Leonard and Penny grapple with getting older, Howard and Bernadette find a surprise in their hot tub and Raj is torn between Emily and the cute girl he met at the Comic Bookstore.
Season 9 | Episode 16 When the gang finds out about Bernadette’s pregnancy, they celebrate by singing karaoke. Also, Bernadette is concerned when Wolowitz freaks out over her pregnancy announcement, and Wolowitz is convinced he must make more money to provide for the baby.
Season 9 | Episode 17 After more than nine years together, the gang finally celebrates Sheldon’s birthday, surprising him with a special guest.
Season 9 | Episode 18 Leonard, Sheldon, and Wolowitz run into problems when they file for a patent for their infinite persistence gyroscope. Also, Penny, Amy and Bernadette give Koothrappali dating advice when Emily reaches out to him after their breakup.
Season 9 | Episode 19 Amy is shocked at a revelation from Sheldon after she buys him a new laptop. Also, Koothrappali sells out Leonard and Wolowitz after they lie to their wives in order to attend an early screening of a movie.
Season 9 | Episode 20 Sheldon spills a secret of Leonard’s when the two take a weekend cabin trip with Penny and Amy. Also, when Koothrappali goes overboard with pregnancy gifts, Wolowitz and Bernadette must draw the line.
Season 9 | Episode 21 Everyone must choose sides when a small argument between Leonard and Sheldon erupts into a heated fight during a group get-together.
Season 9 | Episode 22 The gang goes to a wine bar and runs into Penny’s old boyfriend, Zack. Also, Bernadette gets stuck spending the evening with Sheldon when she can’t go wine tasting with the group, and things don’t go as planned when Koothrappali introduces his new girlfriend, Claire.
Season 9 | Episode 23 Sheldon hires Stuart to spend the day with Amy when he’d rather go to a movie screening. Also, Leonard’s mother, Beverly, comes to town and Penny struggles to make a connection with her.
Season 9 | Episode 24 Chaos ensues when Leonard’s recently divorced parents, Alfred and Beverly, and Sheldon’s devoutly religious mother, Mary, come to town. Also, Wolowitz and Koothrappali think the government is out to get them when they are contacted about their guidance system.