The Big Bang Theory Episode Rating Graph

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

When Leonard receives an exciting opportunity to work overseas, Penny and Sheldon are thrown for a loop. Raj and Lucy's relationship comes to a crossroad.

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.

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.

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

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.

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.

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.

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.

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

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.

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.

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, Howard and Raj try to relive the good old days after Howard buys a scooter that looks like the one he had years ago.

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

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.

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.

Leonard, Penny and Raj adjust to their new living arrangement, and Sheldon takes an interest in Amy’s work.

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.

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.

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

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

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.

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.

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.

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

When Sheldon and Amy build a blanket fort, they come to major crossroads in their relationship. Also, Howard meets the half-brother he never knew he had. Meanwhile, Penny is invited to appear on Wil Wheaton’s podcast, but things turn awkward when Leonard joins them.

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

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.

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.

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 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?"

Penny and Leonard organize a paintball game that results in mayhem when Sheldon is jealous of Amy. Also, Raj catches Anu with her ex-boyfriend, and Stuart gets cold feet when Denise hints at the possibility of them living together.

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.

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

A squabble between Leonard and Penny sees Sheldon playing mediator, though out of his own incovenience from the sitiation rather than altruism.

Johnny Galecki and Kaley Cuoco will lead fans on a trip down memory lane, sharing some of the best-kept backstage secrets and personal memories from the past 12 years.

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.

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.

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

Howard and Raj visit a Goth nightclub to pick up women while Sheldon attempts to build a better Penny using chocolate-based behavior modification.

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.

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 gets into trouble when he snoops around Emily's apartment.

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.

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.

When Amy gets sick, Sheldon tries to nurse her back to health; Wolowitz and his father-in-law plan a fishing trip.

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.

Sheldon creates a monster when he introduces Penny to online gaming.

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.

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.

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.

Leonard asks Penny for advice when his new relationship starts moving too fast.

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

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.

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.

A fight between Sheldon and Penny leaves Amy caught in the middle, while Leonard tries to spice up his long-distance relationship with Priya.

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

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 causes opportunity and conflict at the Wolowitz home.

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

A cute comic book artist puts Leonard and Priya’s relationship to the test, while Sheldon tries to scare the guys for Halloween.

Penny runs into her ex-boyfriend, Zack, who invites her and Leonard to a dinner to meet his newlywed wife. After the dinner the newlywed couple make an odd proposition to Leonard, which makes Penny to freak out. Also, Raj attempts to mend things with his ex-fiancée, Anu.

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.

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. Also, Bernadette gets one of her drugs approved at work and wants a reluctant Penny to head the sales team.

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

When Leonard and Penny aren't speaking, Sheldon goes to extremes to keep them both happy.

Sheldon's search for the answer to a physics problem leads him to work at the Cheesecake Factory with Penny.

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.

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.

Penny plays Matchmaker for Raj, which results in him finding a girl he is comfortable talking to.

The girls decide to re-enact their high school proms with the guys. While Sheldon feels under pressure to commit to his relationship with Amy, Howard worries about who Stuart will bring as his date.

Raj gets an inflated ego and makes a play for Penny after being referenced in a magazine article.

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

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.

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.

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. Bernadette turns into a pageant mom when she tries to help Howard ace his Magic Castle audition.

Leonard and his friends stage an intervention to force Sheldon to face his fear of driving.

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.

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

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. Meanwhile, Leonard and Penny seek advice from Howard and Bernadette after they fight about money.

With Leonard, Howard and Raj away camping in the desert, an injured Penny has only Sheldon to rely on.

Penny starts dating Leonard's handsome colleague; Leonard and his friends are tortured by Sheldon's obsession with gift-giving etiquette.

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. Meanwhile, Howard learns that Bernadette wasn't the only waitress at the Cheesecake Factory who had a crush on him.

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.

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

Sheldon is thrilled when Leonard starts dating a woman who meets Sheldon's stringent standards.

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.

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.

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.

Sheldon winds up in traffic court when he gets a ticket because of Penny.

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.