During a group gathering, a disagreement between Leonard and Sheldon turns into a battle royal, forcing everyone to choose sides.

Sheldon stays behind to spend quality time with the pregnant Bernadette when the rest of the gang toddles off to a wine-tasting event, where they run into Penny's former boyfriend, and Raj introduces his new girlfriend.

When Sheldon decides he'd rather go to a movie screening than hang out with Amy, he hires Stuart to spend the day with her. Meanwhile, Leonard's mother visits, and Penny just can't seem to connect with her.

In the Season 9 finale, Leonard's recently divorced parents roll into town, as does Sheldon's holy-roller mother, and all hell breaks loose. Meanwhile, Raj and Howard are concerned when the government unexpectedly contacts them about their guidance system (more…)In the Season 9 finale, Leonard's recently divorced parents roll into town, as does Sheldon's holy-roller mother, and all hell breaks loose. Meanwhile, Raj and Howard are concerned when the government unexpectedly contacts them about their guidance system.

In the Season 10 premiere, the gang deals with the awkward aftermath of an overnight liaison between Sheldon's mother and Leonard's father. Meanwhile, Penny's dysfunctional family is in town for the wedding, including her neurotic mom and drug-dealer broth (more…)In the Season 10 premiere, the gang deals with the awkward aftermath of an overnight liaison between Sheldon's mother and Leonard's father. Meanwhile, Penny's dysfunctional family is in town for the wedding, including her neurotic mom and drug-dealer brother.

The guys' heads are in a spin when an Air Force bigwig approaches them about their revolutionary gyroscope invention; and Bernadette is upset with Penny after she accidentally leaks a secret to the mom-to-be's coworkers about her being pregnant.

Howard and Leonard are putting in late nights at work and Sheldon is having trouble keeping up; Raj and a pregnant Bernadette spend a day together; and Penny and Amy take in a faculty party.

Season 9 premiere, Penny has a problem dealing with Leonard's confession about having kissed another woman, while Sheldon is confused about Amy calling a timeout on their relationship.

To ease Penny's mind, Leonard pays a visit to the woman he kissed during his expedition to the North Sea, while Sheldon's breakup with Amy leads him to retaliate by shooting a special episode of "Fun With Flags." Later, Bernadette is wracked with guilt ove (more…)To ease Penny's mind, Leonard pays a visit to the woman he kissed during his expedition to the North Sea, while Sheldon's breakup with Amy leads him to retaliate by shooting a special episode of "Fun With Flags." Later, Bernadette is wracked with guilt over withholding a secret from Penny.

The guys surprise Leonard with a belated bachelor-party weekend in Mexico, but their plans hit a bump in the road when they get a flat tire on the way. Meanwhile, the girls lean on Penny to tell her unsuspecting family that she and Leonard eloped.

Sheldon reverts back to 2003 when he learns that Leonard and Penny are moving in together. Meanwhile, Howard and Raj form a band to play at the comic-book store.

When Barry Kripke gives the guys fencing lessons, he makes a point of letting Sheldon know he's interested in dating Amy. Also, Stuart has trouble getting female customers at the Comic Book Store, so Penny, Amy and Bernadette stop by to help out.

A helium shortage leads Sheldon and Leonard to do business with a dealer in the black market in order to acquire some of the element for an experiment they need to complete. Meanwhile, Penny and Bernadette download a dating app on Amy's phone in hopes that (more…)A helium shortage leads Sheldon and Leonard to do business with a dealer in the black market in order to acquire some of the element for an experiment they need to complete. Meanwhile, Penny and Bernadette download a dating app on Amy's phone in hopes that she'll connect with a new man.

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.

Sheldon's interview for a "Star Trek" documentary focusing on Spock turns up a shocking revelation about his breakup with Amy. Meanwhile, the Wolowitzes haggle over the remodeling of his family home.

When Leonard, Penny and Bernadette learn that Amy is going out on a dinner date, the trio set out to spy on her and the guy. Meanwhile, Sheldon recruits Raj and Howard to find a woman for him, since they were responsible for getting Amy and him together.

Now just friends, Sheldon and Amy spend Thanksgiving at the aquarium; a reluctant Wolowitz volunteers at a soup kitchen with Bernadette, Raj and Emily; and Penny realizes that Leonard knows a bit more about her than he's let on.

God only knows what song is constantly playing in Sheldon's head, but it reminds him of Amy and leads to a surprising revelation. Meanwhile, she is back in the dating game; and Raj and Howard go on a quest to find the only fan of their band, Footprints on (more…)God only knows what song is constantly playing in Sheldon's head, but it reminds him of Amy and leads to a surprising revelation. Meanwhile, she is back in the dating game; and Raj and Howard go on a quest to find the only fan of their band, Footprints on the Moon.

Prof. Proton visits Sheldon in a dream and gives him Obi-Wan Kenobi-like advice about whether to go see the new "Star Wars" film or spend the time with newly reunited girlfriend Amy on her birthday. Meanwhile, Leonard, Howard and Raj try to decide who will (more…)Prof. Proton visits Sheldon in a dream and gives him Obi-Wan Kenobi-like advice about whether to go see the new "Star Wars" film or spend the time with newly reunited girlfriend Amy on her birthday. Meanwhile, Leonard, Howard and Raj try to decide who will get their extra ticket to the movie premiere.

Penny entices Leonard to meet with a psychiatrist and the results are surprising; Stuart moves out of the Wolowitz house and Howard and Bernadette find themselves at a loss. Also, in a once-in-a-blue-moon occasion, Sheldon teams with Raj on an astronomical (more…)Penny entices Leonard to meet with a psychiatrist and the results are surprising; Stuart moves out of the Wolowitz house and Howard and Bernadette find themselves at a loss. Also, in a once-in-a-blue-moon occasion, Sheldon teams with Raj on an astronomical discovery.

Dealing with an under-the-weather Sheldon is so draining for Penny, Leonard and the gang that they decide to treat themselves to a Sheldon-less weekend.

Leonard and Sheldon's apartment is robbed, so they create an elaborate security system with the help of their friends.

Newton had his apple. Sheldon has cheesecake. An impasse in his work leads Sheldon to get a job working with Penny at a restaurant known for that dessert.

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.