When the guys find a ring from "The Lord of the Rings" at a garage sale, it threatens to tear them apart.

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.

Raj attempts to cure his social anxiety disorder while Penny uses Bernadette to spy on Leonard and his girlfriend.

When Howard finally breaks the news to his mom that he's engaged to Bernadette, it lands her in the hospital.

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.

Leonard and Amy get to know each other better, while Howard and Bernadette spend the weekend with Mrs. Wolowitz.

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.

Amy becomes heartbroken when she discovers that Penny and Bernadette went wedding dress shopping without her.

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.

Sheldon's selfish demands force Leonard to reconsider their friendship. Meanwhile, Wolowitz tries to pick his astronaut nickname.

After the guys throw Howard a bachelor party, Bernadette reconsiders marrying him after learning about his sexual history.

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.

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.

The gang celebrates Halloween at Stuart’s comic book store. Meanwhile, Leonard seduces Penny with science.

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.

When the University reassigns Sheldon’s parking spot to Wolowitz, their fight affects the whole gang.

During a Dungeons and Dragons game, Sheldon revisits Christmas memories; Amy, Penny and Bernadette look for a date for Raj.

When Sheldon is accused of sexual harassment, he ends up getting Raj, Leonard and Howard in trouble.

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.

A fight between Sheldon and Leonard impacts Amy and Penny's living arrangements; while Howard is away, Raj helps Mrs. Wolowitz out.

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

The girls get involved when Leonard, Sheldon and Raj compete for tenure at the University.

Leonard and Sheldon's friendship is tested; Howard's latest foray into helping his mother has some disastrous side effects.

When the entire gang competes in a scavenger hunt designed by Raj, it brings out the best - and worst - in everyone.

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.

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.

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

While Sheldon is at home in Texas, the rest of the gang realizes how much he has changed their lives as they decorate the apartment Christmas tree.

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. Also, Amy receives an unwanted attention from a co-worker.

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 try to feel more mature by going to a fancy hotel for tea.

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.

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.

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.

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 caretaker for his mother. With his entire world changing around him, Sheldon considers a major move.

Sheldon is forced to teach a class as a Junior Professor and Howard decides to enroll in it. Meanwhile, Amy plays both sides when tension arises between Penny and Bernadette.

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.

Howard 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.

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

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.

As a joke, Sheldon and Penny try an experiment designed to make participants fall in love. Meanwhile, 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.

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.

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.

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 on her.

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".

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.

After having to deal with a sick Sheldon, Leonard, Penny and the gang try to treat themselves to a Sheldon-free weekend.

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.

After more than nine years together, the gang finally celebrates Sheldon’s birthday, surprising him with a special guest.

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.

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.

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

Colonel Williams, an Air Force representative from the Department of Material Command sits down to talk with Wolowitz.

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.

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

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.

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.

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.

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

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.

The gang is concerned when Sheldon’s former admirer, Dr. Ramona Nowitzki, resurfaces while Amy is away at Princeton.

In the eleventh season opener, Amy gives Sheldon an answer to his proposal while Howard and Bernadette struggle with some unexpected news.

Sheldon and Raj confide in Bernadette when they can't handle Amy and Howard working together on a science project. Also, Penny and Leonard learn new tactics for how to deal with Sheldon from an unlikely source.

Leonard and Howard 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 that Ruchi might be trying to take over her projects at work.

Raj and Howard's feud continues as the gang plan Halley's first birthday party. Sheldon's surprise for Amy's birthday goes awry when they get food poisoning. Also, Leonard gets a Christmas letter from his brother that causes him to spiral out about his own lack of accomplishments.

Raj 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.

When Bernadette won't go into labor, the gang tries different tactics to get things started. Also, Howard confronts Bernadette after Amy accidentally reveals she's already chosen their son's name.

Bill Gates visits Penny's work, and the gang schemes to meet him. Hilarity ensues. Meanwhile, Sheldon is convinced that he's a target of an April's Fools prank.

Sheldon’s comic book store experiences changes when writer Neil Gaiman puts Stuart’s store on the map. Also, friendships are threatened when Raj takes credit for Penny's astronomical discovery.

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, Howard and Raj with pinkeye.

Sheldon and Amy's honeymoon runs aground in New York. Penny and Leonard discover they are uncomfortably similar to Amy's parents. Raj insults physicist Neil deGrasse Tyson and starts a Twitter war.

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. Raj doesn’t want Howard to join him in hosting a show at the planetarium.