Episode 1 / The Matrimonial Momentum

In the ninth season premiere, Penny struggles with Leonard's confession that he kissed another girl while on the North Sea. After driving to Vegas, Penny must now decide whether she wants to go through with the wedding. Back home, Sheldon doesn't know how to act after Amy pushes pause on their relationship.

Episode 2 / The Separation Oscillation

After Amy breaks up with Sheldon, he tries to retaliate by filming a special episode of "Fun with Flags." Leonard, meanwhile, confronts the woman he kissed on the North Sea in an attempt to put Penny's mind at ease, and Bernadette feels guilty about withholding a secret from Penny.

Episode 3 / The Bachelor Party Corrosion

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

Episode 4 / The 2003 Approximation

When Penny and Leonard announce they're moving in together, Sheldon decides to revert back to 2003 — a simpler time before he met either of them. Meanwhile, Howard and Raj form a band to play at the Comic Book Store.

Episode 5 / The Perspiration Implementation

When the guys take fencing lessons from Barry Kripke (recurring guest star JOHN ROSS BOWIE), Sheldon finds himself in an awkward position when Kripke expresses interest in Amy. Also, Stuart struggles to bring in female customers are the Comic Book Store, so Penny, Amy and Bernadette come by to help him out.

Episode 6 / The Helium Insufficiency

In the midst of a nationwide helium shortage, Sheldon and Leonard take desperate measures to obtain the supplies they need on the black market. Meanwhile, Penny and Bernadette download a dating app on Amy's phone in order to find her a new man. MICHAEL RAPAPORT guest stars as their Black Market dealer, Kenny.

Episode 7 / The Spock Resonance

While being interviewed for a documentary about Spock, Sheldon struggles to suppress his emotions about his recent break-up with Amy — leaving Leonard and Penny shocked to discover that Sheldon had an engagement ring for Amy. Meanwhile, Howard and Bernadette disagree over remodeling his childhood home. WIL WHEATON, ADAM NIMOY and STEPHEN MERCHANT guest star.

Episode 8 / The Mystery Date Observation

With Amy out on a date with a mystery man, Sheldon enlists the help of Howard and Raj to find a new girlfriend by posting online. And when Amy is coy with the details about the guy she's dating, Penny and Bernadette decide to spy.

Episode 9 / The Platonic Permutation

Sheldon and Amy try hanging out as friends when they spend Thanksgiving together at the Aquarium. Meanwhile, Howard reluctantly agrees to volunteer at the soup kitchen with Bernadette, Raj and Emily, while Penny discovers that Leonard knows more about her than she thought.

Episode10 / The Earworm Reverberation

After driving Leonard and Penny crazy by his desperate attempts to remember the name of a song stuck in his head, Sheldon has a revelation when he realizes why. Then, despite their previously awkward date, Amy invites Dave (recurring guest star STEPHEN MERCHANT) over for dinner. And Howard and Raj become obsessed with a fan of their band, Footprints on the Moon.

Episode 11 / The Opening Night Excitation

After more than five years of dating, Sheldon and Amy spend their first night together; while Leonard, Howard and Raj must decide who will take their extra Star Wars movie ticket. Recurring guest star BOB NEWHART returns as Sheldon's Obi-Wan to advise him on his difficult relationship decisions.

Episode 12 / The Sales Call Sublimation

Penny gets more than she bargained for when Leonard agrees to meet with a psychiatrist on her behalf. Sheldon and Raj collaborate on an astronomical discovery. Howard and Bernadette can't believe what they're feeling after Stuart moves out.

Episode 13 / The Empathy Optimization

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

Episode 14 / The Meemaw Materialization

Sheldon's thrilled when his Meemaw (guest star JUNE SQUIBB) comes to visit, but his excitement quickly fades when she butts heads with Amy. Also, Raj meets a new girl (guest star ALESSANDRA TORRESANI) at the comic book store who makes him question his relationship with Emily.

Episode 15 / The Valentino Submergence

Sheldon and Amy host a special live Valentine's Day episode of "Fun with Flags." While 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 Book Store.

Episode 16 / The Positive Negative Reaction

When the gang finds out about Bernadette's pregnancy, they celebrate by singing karaoke. Meanwhile, Bernadette is concerned when Howard freaks out over her pregnancy announcement, as he's convinced that he needs to make more money to provide for the baby.

Episode 17 / The Celebration Experimentation

After more than nine years together, the gang finally celebrates Sheldon's birthday with a few special guests on the 200th episode. CHRISTINE BARANSKI, SARA GILBERT and WIL WHEATON return and are joined by special guest star ADAM WEST.

Episode 18 / The Application Deterioration

Leonard, Sheldon and Howard run into problems when they file for a patent for their infinite persistence gyroscope. Meanwhile, Penny, Amy and Bernadette give Raj dating advice after Emily reaches out to him after their breakup.

Episode 19 / The Soldier Excursion Diversion

When Sheldon's laptop dies, it leads him to share a deep secret with Amy after she buys him a new one; Meanwhile, Raj sells out Leonard and Howard after they lie to their wives in order to attend an early screening of a movie.

Episode 20 / The Big Bear Precipitation

Sheldon spills a secret of Leonard's when the two take a weekend cabin trip with Penny and Amy; Meanwhile Howard and Bernadette must draw the line when Raj goes overboard with pregnancy gifts.

Episode 21 / The Viewing Party Combustion

When a small argument between Leonard and Sheldon erupts into a heated fight, everyone must take sides during a group get-together.

Episode 22 / The Fermentation Bifurcation

The gang goes to a wine bar and runs into Penny's old boyfriend, Zack (recurring guest star BRIAN THOMAS SMITH); 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 Raj introduces his new girlfriend, Claire (ALESSANDRA TORRESANI).

Episode 23 / The Line Substitution Solution

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.

Episode 24 / The Convergence Convergence

Chaos ensues in the ninth season finale when Leonard's recently divorced parents (special guest stars JUDD HIRSCH and CHRISTINE BARANSKI) and Sheldon's devoutly religious mother come to town. Meanwhile, Howard and Raj think the government is out to get them, when they're contacted about their guidance system.