The Big Bang Theory

Leonard is concerned when his date with Penny ends abruptly and she starts blowing him off. When told the truth, Sheldon would rather move out than keep Penny's reasons a secret from Leonard.

After seeing Penny with her new boyfriend, Leonard turns to Leslie for comfort. The move angers Sheldon, who considers Leslie his comic book-style “arch enemy.”

Sheldon turns Penny on to online gaming, and then she refuses to turn it off after becoming addicted.

After being featured in a People magazine article, Raj becomes full of himself and alienates his friends. However, his newfound fame does get him a date with Penny.

The gang tries to teach Sheldon how to drive.

Sheldon becomes cozy with a female graduate student who is infatuated with him, but nobody can figure out whether they're in a relationship–including Sheldon.

Penny plans revenge when Sheldon bans her from the guys' apartment, while Howard and Rajesh use the latest technology to try to find the house being used in “America's Next Top Model.”

Howard and Leonard's friendship could be at an end when Leonard steals Howard's new woman from him.

Sheldon tries to help move Leonard's new relationship along, because his track record with women has been less than successful. But will he cause more trouble than good?

Leonard is the last one to realize that Stephanie has moved in with him. And when he finds out, he becomes worried that they are moving too fast

Much to Lenonard's disappointment, Penny suddenly develops an interest in science when a sexy new physicist joins the lab. Meanwhile, Sheldon struggles to find an appropriate Christmas gift for Penny.

Howard becomes depressed after Penny makes a cruel statement about his love life, while the rest of the guys prepare for a grudge killer robot duel against an obnoxious colleague at the university.

Sheldon tries to make friends with a despised colleague, with the hopes that it will get him access to a coveted computer in the lab.

Penny cannot afford to pay her rent, so Sheldon and Leonard each come up with unique ways to help her out.

Sheldon hits it off with Leonard's psychoanalyst mother, but she drives Leonard and Penny to the bottle.

Howard hooks up with Leslie, while Penny accidentally ruins Sheldon's spot on the couch.

On a train trip to San Francisco, the boys debate on how to meet sci-fi star Summer Glau, who is on board with them.

Sheldon's assistance with Penny's home-based business leads to disaster.

Penny becomes jealous when a gorgeous new neighbor attracts the guys' attention.

Leonard is so upset when a friend from the comic book store begins dating Penny that he convinces Howard and Raj to take him to a bar so that he can pick up a woman of his own.

After being dumped by Leslie, Howard heads to Las Vegas with Leonard and Raj, leaving Penny to deal with Sheldon, who has locked himself out of the apartment.

Penny's second date with Stuart has significant implications for Leonard. Howard enlists the guys' help with one of his NASA projects.

After returning from the North Pole, a conflict among the guys sends Sheldon back to Texas and interferes with Leonard's reunion with Penny.

Leonard and Penny's first night together goes awkwardly. Sheldon and Howard wager on the species of a cricket.

Sheldon attempts to covertly alter Penny's habits, while Howard and Raj try their luck meeting women at a Goth-style club.

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 third wheel.

Wolowitz begs Penny to set him up with one of her friends; Sheldon seeks payback against Wil Wheaton.

To blend in better with several of Penny's friends from back home, Leonard learns about football…from Sheldon. Meanwhile, a loss in a kite war threatens to end Raj and Howard's friendship.

Sheldon is forced to play peacemaker when Leonard and Penny have an argument, mainly because their fighting is bringing back repressed childhood memories.

Penny separates her shoulder in the bathtub, and is forced to turn to Sheldon for help. Meanwhile, the rest of the guys accidentally get stoned in the desert while waiting for a meteor shower

Sheldon vows payback after Kripke humiliates him on the radio. Howard gets advice concerning his relationship with Bernadette…from “Battlestar Galactica's” Katee Sackhoff.

Sheldon attempts to help Penny understand physics to impress Leonard, and Wolowitz becomes jealous when his new girlfriend takes an interest in Leonard's research.

Leonard's mother makes a visit to his dismay and Sheldon's delight.

Raj talks Sheldon into being his wingman at a university mixer. Leonard has trouble dealing with Penny consulting a psychic.

When their apartment is robbed, Leonard and Sheldon turn to their friends to create a state-of-the-art security system.

Sheldon acts even more strangely when he is stumped by a difficult physics question, so he is forced to resort to Einstein-inspired measures to unclutter his mind and solve the problem.

When Leonard must travel to Switzerland on Valentine's Day to visit the CERN laboratory, Sheldon uses any and all means to be his guest instead of Penny.

Sheldon misses an opportunity to get Stan Lee's autograph because he has to make an appearance in traffic court.

When the guys find an actual ring from the “Lord of the Rings” trilogy at a garage sale, their friendship is threatened.

Sheldon needs the gang's help in overcoming his fear of public speaking when he receives an award.

Sheldon takes on his newest nemesis, Star Trek's Wil Wheaton, in bowling. Leonard and Penny's relationship comes to a crossroad.

With Leonard and Penny now broken up, Sheldon is forced to go behind Leonard's back to spend time with her.

Sheldon and Penny are both disturbed and disappointed when Leonard hooks up with Sheldon's visiting female physicist friend.

After Leonard and Sheldon get in a fight over the thermostat, Leonard goes to Penny's apartment and tells her about how he met Sheldon for the first time and how they became roommates…and what happened to the elevator.

Penny ends up tagging along on Sheldon's first-ever date with Amy Farrah Fowler, while Wolowitz finds an unusual use for the new robotic arm he's created.

When Sheldon calculates the technology to download his consciousness into a robot won't be invented soon enough, he desperately tries to find a way to increase his lifespan.

Following his breakup with Amy, the gang becomes concerned with Sheldon's obsessive search for non-human companionship, and they call his mother to intervene.

Wolowitz tries to get help from Penny, Katie Sackhoff and George Takei to get back together with Bernadette, while Raj and Sheldon quarrel over office space as they work together on a project

Sheldon is scared that he is in a relationship when Amy asks him to meet her mother, and Leonard asks Wolowitz and Bernadette to set him up because he is the only person in the group without a girlfriend.

Leonard tries to keep everyone from finding out that he spent the night with Raj's sister, but Sheldon finds out and concocts an elaborate story to help him keep the secret from Raj.

An FBI agent interviews everyone when Howard needs to obtain a security clearance. Sheldon is beside himself when Howard refuses to accept his apology.

The guys camp out all night waiting to see a new movie while Penny and Bernadette invite Amy to her first slumber party.

Penny asks Leonard to pose as her boyfriend when her father visits. Howard, Raj, and Bernadette are up all night looking through a telescope.

Amy finds she has sexual feelings for Penny's ex, while Koothrappali and Wolowitz try to prove who would be the better superhero.

The guys enter a costume contest as members of the Justice League…and convince Penny's new boyfriend to join them.

Leonard has an idea for a new smartphone app and asks the guys for help. However, Sheldon tries to take over the project, and Leonard fires him.

Tension runs high as the entire gang spends the weekend together at a science convention.

To improve his skills as an instructor, Sheldon asks Penny to give him acting lessons. Meanwhile, Raj begins having impure fantasies about Bernadette.

To secure needed funding for their school, Sheldon convinces Leonard to get friendly with a wealthy benefactor.

Bernadette makes Howard choose between herself and his mother, and how will Penny react when Leonard begins seeing Raj's sister again when she's back in town?

Sheldon becomes concerned when everybody begins to hang out at Raj's apartment and discovers Leonard is the center of the group.

Priya forces Leonard to choose between a relationship with her or a friendship with Penny. A magic trick by Howard has Sheldon fooled.

The gang goes all out to help Sheldon find the person responsible for hacking his online gaming account, but Priya is beginning to get fed up with Leonard's childish behavior.

Sheldon and Amy secretly experiment on the gang by spreading rumors. Howard and Bernadette's relationship reaches an important milestone.

When Priya finds a loophole in the roommate agreement to throw Sheldon out for the night, Penny, Amy, and Bernadette take Sheldon to a nightclub.

While Sheldon invents a three-player chess game, Bernadette uses a double date to spy on Leonard and Priya's relationship, and Raj tries a new drug to treat his social anxiety.

Howard believes that his mom suffered a heart attack because he told her that he's marrying Bernadette, and Sheldon freaks out over germs after he accidentally drinks Leonard's water.

The gang deals with the fallout from Penny and Raj's night together. Amy counsels Penny when she considers moving back to Nebraska due to her failing acting career. Sheldon takes charge of the paintball team.

Sheldon has health issues with Penny's new chair. Amy gets inadvertently caught in the middle of a fight between Sheldon and Penny. Leonard tries to add some spice to his long-distance relationship with Priya.

While Sheldon stays at home to play with his new train set, Leonard and Amy learn a lot about each other when he goes as her “plus one” to a wedding. Howard and Bernadette spend the weekend with his mother.

Penny sets up Raj with a deaf friend, not knowing that she's actually a gold digger, and Sheldon decides to let his minor decisions rest on the roll of the dice.

Sheldon takes offense when Leonard wants to attend a party with Star Trek's Wil Wheaton and Brent Spiner, and Bernadette tries to block Howard's opportunity to go into outer space.

Sheldon is upset when his mom comes to visit but refuses to cook for him and attend physics lectures.

Sheldon tries to get into the spirit of Halloween by trying to scare the guys after they prank him. A comic book artist is interested in Leonard.

Amy is hurt when Bernadette and Penny goes bridesmaid dress shopping without her, so she turns to a reluctant Sheldon for comfort.

Sheldon must overcome his fear of birds while Leonard and Penny attempt to hang out together strictly as friends.

When Stuart from the comic book store asks Amy on a date, Sheldon considers having a more serious relationship with her. Meanwhile, the guys become obsessed with a new card game involving Wild West heroes and witches.

Leonard must confront the man who bullied him in high school, while Penny realizes she did her fair share of tormenting in the past.

Penny must help Sheldon work on his relationship with Amy when he trivializes one of her accomplishments. Bernadette's dislike of children bothers Howard.

Leonard and Penny contemplate reviving their romantic relationship. Sheldon's attempt to order Star Trek memorabilia doesn't go as planned.

Leonard and Penny develop a system to insure their dates go smoothly. Raj finally finds a woman he can talk to - the virtual assistant on his mobile phone.

Leonard signs out of his roommate agreement, reducing himself and Sheldon to mere acquaintances, while Howard tries to think of a cool astronaut nickname for himself.

When the university forces Sheldon to use vacation days, he decides to hang out in Amy's lab. Bernadette wants Howard to sign a prenuptial agreement.

Sheldon battles Barry Kripke for a coveted office at the university. Penny receives a very unusual gift from Amy.

Sheldon wreaks havoc when he tries to get a haircut from his regular barber, who is ill. Howard runs into a few problems with astronaut training.

Sheldon must choose between joining Amy at her aunt's birthday party or playing videogames all weekend with the guys.

Raj gets quite a surprise when he asks his parents to set him up on a date. Penny buys Leonard and Sheldon a pair of Star Trek keepsake collectibles, not knowing the effect it would have on Sheldon.

Sheldon uses any and all means to meet his hero, Dr. Stephen Hawking.

The guys throw Howard a bachelor party, and some embarrassing details about his life get posted on the Internet.

Howard faces double trouble when NASA moves up his launch and he has to meet Bernadette's father. Some awkward pillow talk by Leonard may change his relationship with Penny.

When Sheldon is required by the Relationship Agreement to take Amy out for their second anniversary, he asks Raj to tag along. Leonard has difficulty being with Penny and not asking where their relationship is heading.

The gang wants Penny to tell Leonard how she feels about him. Howard is the target of practical jokes on the space station. Raj and Stuart plan to go out on the town.

When Sheldon hires a female grad student to assist him, a jealous Amy asks Penny to help her spy on them, only to make a shocking discovery. Life in the International Space Station is wearing on Howard.

Howard is offended when his return from space is met with little fanfare but he gets an even bigger surprise at home. Game Night turns into a battle royale between Penny and Sheldon.

When the gang celebrates Halloween at Stuart's comic book store, Leonard uses his scientific knowledge to seduce Penny.

Penny enrolls in a college class and keeps it a secret from Leonard. Sheldon causes conflict with Dr. Stephen Hawking over an online game.

Wolowitz must make a decision whether or not to move out of his mother's house, and Sheldon is caught in the middle of an argument between Amy and Wil Wheaton.

Leonard is surprised to learn about Penny's study partner at school, and Howard and Raj are determined to find out about one of Sheldon's secrets.

The gang is drawn into a fight between Howard and Sheldon over Sheldon's vacant parking spot.

Howard tries to bond with Bernadette's father during a fishing trip. When Sheldon is obligated to take care of a sick Amy, she finds ways to take advantage of the situation.

Sheldon revisits some Christmas memories during a game of Dungeons and Dragons, while Penny, Bernadette and Amy try to find a girl for Koothrappali when he joins the girls for ladies' night.

When Sheldon gets accused by the university of sexual harassment, he gets the other guys in trouble, too.

Leonard, Sheldon, Howard and Raj head to Bakersfield for a local Comic-Con event. Driving on the way, they decide on the spur of the moment to stop at Vasquez Rocks where many episodes of <a href=“/title/tt0060028/”>Raumschiff Enterprise</a> were filmed, there where they can get into their Star Trek costumes and pretend to be on the show. Their stop doesn't end up being quite what they expect, which leads to a surprising reaction from the group about their comic book focus. Meanwhile, Penny, Bernadette and Amy ponder why the guys are so enthralled with comic books. As such, the females head to the comic book …

Sheldon is forced to work on a project with Barry Kripke. Raj and Howard spend big bucks trying to get superhero figurines made of themselves.

After one insensitive and self-serving move too many by Sheldon, Leonard has had it with him and decides to move out, even throwing the roommate agreement into the garbage. While Sheldon doesn't understand or want Leonard to move out (although Sheldon will not apologize for what he sees as no wrongdoing on his part), he doesn't believe Leonard has anywhere to go. Unilaterally, Leonard decides to move in with Penny, who doesn't have the confidence to tell him that she doesn't want him to move in since she doesn't believe their relationship is yet at that stage. With an…

Sheldon tasks his assistant to buy a Valentine's Day gift for Amy. Leonard, Penny, Howard, and Bernadette have a disastrous dinner together, while Raj and Stuart host a “Lonely People” party at the comic book store.

Raj and Lucy have coffee together after they meet at the comic book store and get along until she unexpectedly runs off. Raj gets depressed and won't leave his apartment. Sheldon has Penny as a guest on “Fun with Flag” honoring the flag of her home-state, Nebraska. The gang goes to see Penny in her acting class' performance of “A Streetcar Named Desire.” Sheldon is dragged to it and is impressed by Penny's acting skills. Howard takes a note to Raj from Lucy with her phone number on it. They get together and find that both of them have social skill problems and agree …

Raj devises a date for Lucy that fixes their social anxiety problems. Leonard, Sheldon, and Howard give lectures on science to junior high students. Penny, Amy, and Bernadette ditch work to go to Disneyland.

Penny and Leonard host a cocktail party. Howard receives a letter from his father, whom he hasn't heard from since he was 11.

Leonard, Sheldon, and Raj battle for tenure at the university and drag the ladies into the fight.

Sheldon falls apart when one of his favorite TV shows is canceled and Amy must help him through it. Raj finds out a secret about Lucy.

Bernadette and Howard offer to watch Raj's dog and live to regret it. Leonard and Sheldon hire their favorite childhood star, Professor Proton (Bob Newhart), to make an appearance.

A date between Raj and Lucy takes both of them out of their comfort zones. After a trip to Las Vegas goes awry, the ladies join in on a Dungeons & Dragons game, which causes Amy and Sheldon to reevaluate their relationship.

Sheldon and Penny bond over missing Leonard. Howard tries to help Raj get over his breakup with Lucy.

Sheldon feels betrayed when Leonard returns from the North Sea and wants to spend his time with Penny instead of him. Howard's latest foray into helping his mother has some disastrous side effects.

Insanity reigns when the gang participates in Raj's scavenger hunt.

Sheldon gets mad at Amy for ruining one of his favorite movies. Raj & Stuart try to make their online dating profiles more appealing, and Leonard tries to play the sympathy card with Penny.

After a fight with Bernadette, Howard ends up on Raj's couch. Sheldon must balance work and social time when Amy takes a job at the university.

Howard tries to do something special to celebrate the anniversary of his first date with Bernadette. Sheldon is conflicted when he makes a major scientific breakthrough but some details have to be corrected.

Sheldon seeks payback when Leonard asks Arthur “Professor Proton” Jeffries (Bob Newhart) for help on a project instead of him. Raj gets upset at Howard for crashing his night out with the ladies.

Sheldon demands Leonard make up for a mistake from their past. Penny confronts Raj's ex-girlfriend, Lucy.

The gang spends Thanksgiving at Mrs. Wolowitz's house. Howard tries to bond with his father-in-law, and a mistake from Penny's past comes back to haunt her.

Leonard has to deal with the fallout of disproving Sheldon's new scientific discovery. Raj spends a week at Howard's and Bernadette's apartment.

While Sheldon is at home in Texas, the rest of the gang decorates for Christmas and thinks about how much he has affected their lives.

After Leonard tries to help Penny following a failed role on a TV show, she makes an important decision. Raj tries to practice his social skills on his own, and Sheldon navigates the intricacies of being funny.

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.

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.”

Sheldon and Amy take a train ride to Napa Valley with Howard and Bernadette on Valentine's Day. Leonard and Penny take Raj's dog to the vet when she accidentally eats some chocolate.

Leonard's purchase of a dining room table causes Sheldon to reevaluate the changes in his life. Meanwhile, Howard is offered a chance to go back to space and Bernadette struggles with whether or not to encourage him.

After arguing with Sheldon, Howard tries to make amends by taking him to NASA headquarters in Houston. Penny has second thoughts about quitting her waitressing job when her car dies. Amy gets involved in trying to find Raj a date.

When Sheldon visits his mom in Houston, he is forced to confront a new reality. Back in Pasadena, Raj's Murder Mystery party causes conflict for the rest of the gang.

While Raj is wracked with guilt when he tries to date Lucy and Emily at the same time, Penny wrestles with whether to take a role in a cheesy movie and Sheldon is torn trying to choose between two gaming systems.

Penny tries to help Sheldon when he reconsiders his “relationship” with String Theory. During a dinner with Howard and Bernadette, Raj discovers Howard once embarrassed himself on a date with Emily.

When Sheldon tries to be spontaneous, it leads to unexpected friction between Penny, Amy and Bernadette. Meanwhile, Raj seeks Howard's help in preparing for a date with Emily.

As the gang celebrates Star Wars Day, Sheldon has difficulty dealing with the death of Professor Proton.

Penny gets fired from her movie and takes a serious look at her life. Raj sees Emily on a date with another man at the movies. Howard and Bernadette have to take care of his mother after she breaks her leg.

Leonard and Amy take an unexpected road trip to Arizona to pick up Sheldon. Meanwhile, Penny interviews for a job at Bernadette's company, and Howard is weirded out by Stuart's relationship with Mrs. Wolowitz.

When Sheldon is forced to teach a class, Howard surprises everyone by taking it. Meanwhile, the tension between Penny and Bernadette gives Amy a chance to play both sides.

Howard becomes nervous after NASA asks him to throw out the first pitch at a Los Angeles Angels game. Meanwhile, Leonard and Penny try to prove Sheldon wrong after he says that he and Amy are a ‘superior couple’.

Raj's honesty about his past comes back to haunt him after Emily takes a dislike to Penny. Meanwhile, the guys consider investing in the comic book store.

Amy and Bernadette accuse Penny of being a ‘buzzkill’ after she gets an email from work during their Vegas weekend. Meanwhile, the guys try to invent something cool, but only come up with new ways to procrastinate.

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. Meanwhile, Leonard and Penny seek advice from Howard and Bernadette when they argue about money.

An unhinged doctor has a crush on Penny, but the guys develop a geeky crush on him. Bernadette gets upset when Amy torpedoes an article about her for a local magazine.

When the girls discover none of the guys attended prom in school, they organize one for them, but Howard has a big problem with the woman Stuart asks to go with him.

Sheldon panics when Leonard announces he has to go into the hospital for surgery. Raj discovers his parents have divorced.

While Sheldon retires “Fun With Flags”, Leonard, Howard and Raj look for something significant in a dead professor's research, and Bernadette finds out what her colleagues really think of her.

Amy hosts a traditional Victorian Christmas Eve dinner, Raj's father comes to visit, and the guys try to shoo out a bird they let into the university clean room.

Raj worries a probe he designed will not work in outer space, while Penny and Amy persuade Leonard and Sheldon to go shopping with them.

When Sheldon becomes stuck in a rut with his work, the gang try to help him by raising his stress levels. Howard teases Raj with a game called “Cinnamon or Emily.”

After Bernadette finds Penny's gorilla movie online, Penny manages to find an even more embarrassing video about Bernadette. Leonard and Sheldon upload a paper to the Internet and obsess over someone making negative comments about it.

Howard receives some shocking news as everyone prepares for the re-opening of the comic book store. Meanwhile, Penny tries to teach Sheldon how to “let it go,” but can't follow her own advice when she learns something infuriating about Amy.

Sheldon and Penny agree to participate in an unusual experiment. Meanwhile, Leonard, Amy, Raj and Emily spend the evening trying to escape a room with a “zombie”, and after returning from Mrs. Wolowitz's funeral, Howard and Bernadette run into trouble at the airport.

A trip to the pet store ends in a fight after Amy learns Sheldon has applied for a one-way mission to colonize Mars. Meanwhile, Leonard surprises Penny with a very “adult” purchase, and Raj is caught snooping around Emily's apartment.

Tension arises when a magazine fails to mention Leonard in an article about the paper he co-wrote with Sheldon, and a blackout at Mrs. Wolowitz's home leads to a final family dinner in her honor.

When Leonard and Sheldon are invited to speak at UC Berkeley, they take a detour to try and meet one of their idols. Meanwhile, while cleaning out Mrs. Wolowitz's house, a ping pong battle ensues when Howard and Bernadette argue over the fate of his TARDIS.

When Sheldon and Amy build a blanket fort, they come to major crossroads in their relationship. Meanwhile, Howard meets the half-brother he never knew he had, and Penny is invited to appear on Wil Wheaton's podcast.

When Raj is asked to create a message on the off chance a NASA mission discovers alien life, the guys fight over what he should do, while Penny contemplates returning to acting.

Howard questions his engineering abilities when he and Sheldon can't get a toy drone to fly. A cancelled flight nearly prevents Leonard from giving the commencement address at his former high school. Raj pits his parents against each other when his father cuts him off financially.

Personalities collide when Leonard and Sheldon'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.

Penny struggles with Leonard's confession that he kissed another woman as they prepare to get married in Las Vegas. Meanwhile, Sheldon doesn't know what to do after Amy pushes pause on their relationship.

Leonard confronts the woman he kissed on the North Sea in an attempt to set Penny's mind at ease. Meanwhile, Sheldon films a special episode of “Fun with Flags” after his breakup with Amy, and Bernadette feels guilty about withholding a secret from Penny.

The guys' science skills are put to the test when they get a flat tire during Leonard's bachelor party weekend in Mexico. Meanwhile, the girls force Penny to finally tell her family that she eloped with Leonard.

Leonard and Penny finally move in together leaving Sheldon very upset with this big change in his life and wishing he could go back to a time when he had no emotions in 2003 before he met Leonard. Raj, Howard and Stuart attempt to form a band.

The guys want to learn to be better at sports so Barry Kripke teaches them fencing. Meanwhile the girls help Stuart try to get more women to come to the comic book store. Amy gets asked out by Stuart and Kripke but she turns them both down.

Sheldon and Leonard find out that other scientists are trying to steal their Superfluid Helium idea. The gang try and find a new boyfriend for Amy on a new mobile dating app.

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.

Sheldon recruits Howard and Raj in order to find him a new girlfriend, while Bernadette, Penny and Leonard spy on Amy's mystery date.

On Thanksgiving, Sheldon and Amy try to spend time together as friends and go to an aquarium, Howard 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.

Sheldon can't get a tune out of his head. He can't work out what song it is. Meanwhile, Amy is having Dave over to hers, but Bernadette is reluctant. Howard and Raj meet a fan of their band and Sheldon gives Amy an ultimatum.

Leonard, Wolowitz, and Koothrappali must decide who will take their extra Star Wars movie ticket. After five years of dating, Sheldon and Amy spend their first night together.

Leonard visits a psychiatrist so Penny can make a sales call on her and they learn some things about their interactions and marital issues. Stuart moves out of the Wolowitz House. Sheldon works with Raj looking for extra-solar planets.

After being forced to deal with a sick Sheldon, the rest of the gang try to treat themselves to a Sheldon-free weekend.

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.

Sheldon and Amy host a 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 Claire.

Bernadette has some news to share, but the reactions are not what is expected.

Amy convinces Sheldon to celebrate his birthday for the first time since his childhood. The group plans a birthday party for him, convincing celebrated Batman actor Adam West. But when Sheldon enters the party he is overcome with anxiety.

Sheldon works up a contract to split their portion of their guidance system invention royalties, but Bernadette does not like how it's done. Raj must again decide between Emily and Claire when they both contact him.

Amy is shocked by a revelation from Sheldon when she buys him a new laptop. Raj rats on Leonard and Howard to Penny and Bernadette.

Secrets are revealed when Amy and Sheldon join Penny and Leonard on a weekend cabin trip. Raj is more excited about Howard's and Bernadette's impending parenthood than they are.

Everyone must choose sides when a small argument between Leonard and Sheldon erupts into a heated fight during a group get-together.

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.

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.

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.

The Air Force shows interest in the guidance system and Penny lets it slip at work that Bernadette is expecting.

Sheldon can't keep up with the late nights Howard and Leonard are putting in, Raj spends the day with a pregnant Bernadette and Penny and Amy attend a faculty party.

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

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.

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.

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.

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.

Sheldon and Leonard must divide up their possessions and remove Penny's things from 4B.

Amy's desire to have an intimate night with Sheldon on her birthday is interrupted by Bernadette going into labor.

Sheldon and Amy visit Leonard and Penny for the first time since the holidays and share details about their terrible trip to Texas.

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.

Sheldon uses a machine to help him identify other people's emotions, and Raj tries to understand his difficulties with women.

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.

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.

The guys' annual trip to Comic Con is in doubt when Raj can't afford to go.

When Raj moves out of his apartment, Leonard and Penny offer him Sheldon's old room.

Sheldon and Amy begin to collaborate on a scientific project. Meanwhile, Raj and Penny spend time together doing some of the things Penny loves, which makes Leonard jealous.

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.

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

Sorry, no summary available for this episode!

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.

Amy has trouble deciding whether or not she should marry Sheldon.

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.

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.

Howard and Sheldon build a rocket.

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.

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.

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.

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.

The gang hunts for a “valuable” old laptop.

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.

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.

Sheldon and Amy will try to use science to see who should be their Maid of Honor and Best Man.

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.

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.

Leonard's book raises questions, and Amy guest stars on the new Professor Proton show.

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.

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.

Bill Gates visits Penny's work, and the gang schemes to meet him. Hilarity ensues.

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.

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.

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.

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.

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.

Sheldon and Amy's honeymoon runs aground in New York, while Penny and Leonard discover they are uncomfortably similar to Amy's parents, Mr. and Mrs. Fowler. Also, Koothrappali insults physicist Neil deGrasse Tyson and starts a Twitter war.

Sheldon and Amy drive themselves crazy trying to figure out what “perfect gift” Leonard and Penny gave them for their wedding. Also, Koothrappali decides he wants to settle down and asks his father to arrange a marriage for him.

The Wolowitzes' life gets complicated when Stuart starts bringing his new girlfriend home. Also, Penny and Leonard talk about starting a family while Koothrappali explores an arranged marriage.

When Sheldon won't tell anyone why he's never mentioned Tam, his childhood best friend, Leonard takes matters into his own hands. Also, Bernadette and Penny take out Raj’s fiancée, Anu, for dinner to get the skinny on her.

When Amy doesn’t have time to work on super-asymmetry, Sheldon goes to great lengths to ensure she’s available to work with him even it if means accidentally sabotaging her career in the process. Also, Koothrappali doesn’t want Wolowitz to join him in hosting a show at the planetarium.

When Wolowitz dresses up as Sheldon for Halloween, Sheldon seeks retaliation at Leonard and Penny's Halloween party. Also, Leonard is shocked that Penny doesn't remember their first kiss.

Leonard is caught between a rock and a hard place when he's responsible for distributing extra grant money. Also, Bernadette turns the backyard playhouse into a hideaway from her husband and kids.

Sheldon tries to bond with Amy's father, but when Wolowitz lures Mr. Fowler away with magic tricks, Sheldon has no choice but to bond with Mrs. Fowler; Koothrappali and Anu try to get physical for the first time.

Sheldon and Amy are devastated after learning from a Russian paper that Super Asymmetry has already been discovered and disproven. Also, ultra-competitive Bernadette asks Stuart’s girlfriend, Denise, to teach her how to beat Howard in a popular videogame.

Sheldon and Amy are still down about their theory being disproven, but a VHS tape from Sheldon’s past inspires him not to give up. Also, Bernadette turns into a pageant mom when she tries to help Wolowitz ace his Magic Castle audition.

Penny and Leonard organize a paintball game that results in mayhem when Sheldon is jealous of Amy. Also, Koothrappali catches Anu with her ex-boyfriend, and Stuart doesn’t want to move in with Denise.

Penny’s ex-boyfriend, Zack, and his wife want a baby, but when Zack is infertile, they ask Leonard for help. Also, Koothrappali attempts to mend things with his ex-fiancée, Anu.

Sheldon and Amy are thrilled when their super asymmetry theory is proven by two physicists, until they try to kick Amy off the Nobel nomination; Bernadette has a big success at work.

Sheldon is thrilled to help Bernadette and Wolowitz navigate bureaucratic paperwork, until he discovers they are breaking the law. Also, Leonard is disappointed when his friends exclude him from a scientific project.

Penny tries to seduce an abstaining Leonard to ruin his “donation” for her ex-boyfriend, Zack, and his wife, Marissa. Also, Wolowitz, Bernadette, Anu and Koothrappali turn Koothrappali's canceled bachelor party into a couple's trip.

The gang finds out Wil Wheaton hosts a celebrity Dungeons and Dragons game involving William Shatner, Joe Manganiello, Kareem Abdul-Jabbar and Kevin Smith. Deception and betrayal are the path to make it to the one open seat.

When Penny and Bernadette go to San Diego for a pharmaceutical sales convention, Wolowitz is in charge of the kids. Also, Sheldon finds a book on experimenting on kids, and the guys plus Amy make a day of it.

When competitors Pemberton and Campbell charm America on a publicity tour, Sheldon and Amy try to bring Nobel laureates Kip Thorne, George Smoot and Frances Arnold to their side. Also, Halley's fear of the dark leads to opportunity and conflict for Howard, Bernadette and Stuart.

The concept of what it would mean for women everywhere if Amy were to win a Nobel Prize causes Amy to have a meltdown. Also, Koothrappali and Wolowitz try to relive the good old days after Wolowitz buys a scooter that looks like the one he had years ago.

Koothrappali is worried people won’t take him seriously in his own field after publishing a paper that suggests he may have discovered alien life. Also, Leonard wants to be the principal investigator on a plasma physics study.

Kripke has proof that Dr. Pemberton plagiarized his thesis in college, and Sheldon and Amy aren't sure if they should turn him in or not; Wolowitz learns that Bernadette wasn't the only waitress at the Cheesecake Factory who had a crush on him.

Leonard is pleasantly surprised when Beverly comes to visit and she's genuinely kind to him, until he finds out the real reason she's there. Also, Denise and Stuart overstay their welcome at the Wolowitz house.

Sheldon and Amy are up late waiting for a call from the Nobel Committee. Following a prank call from Kripke, they are told they've won the Nobel Prize in Physics for their super-asymmetry work. The attention from the media and the university bothers Sheldon.

Two months after the events of “The Change Constant”, Sheldon and Leonard repair Sheldon's DNA molecule model as everyone prepares to fly to Sweden for the Nobel ceremony. Howard and Bernadette nervously leave their kids for the first time with Stuart and Denise, while Raj leaves his dog with Bert. Penny has become pregnant, though she and Leonard are keeping it a secret.