4 seasons available
Sheldon struggles to understand what is going on with Amy; Penny must decide if she can get past Leonard's bad behavior.
Leonard tries to ease Penny's mind; Sheldon plans a special episode of "Fun With Flags"; Bernadette feels bad about keeping a secret.
A flat tire during Leonard's bachelor party weekend in Mexico tests the guys' skills; Penny is compelled to tell her family that she and Leonard eloped.
An impending change to his living arrangements inspires Sheldon to revert to 2003, before he met Penny and Leonard; Raj and Howard form a band.
Barry Kripke expresses interest in Amy while leading a fencing lesson for the guys; when Stuart tries to attract female customers to the store, Penny, Amy and Bernadette help out.
Leonard and Sheldon go to great lengths to secure the helium they need during a nation-wide shortage; Bernadette and Penny try to find Amy a new man on a dating app.
A magazine article only credits Sheldon in an article about a paper he co-wrote with Leonard; a blackout at Mrs. Wolowitz's results in a final dinner in her honor.
When Sheldon and Leonard are asked to speak at UC Berkeley, they take a detour in hope of meeting an idol; Raj and Amy try to settle a dispute between Howard and Bernadette with a game of ping pong.
Sheldon and Amy build a blanket fort -- and come to a crossroads in their relationship; Wolowitz meets a half-brother he didn't know he had; Leonard and Penny have an argument during an appearance on Wil Wheaton's podcast.
The guys fight over what message Raj should write for NASA in case of alien contact; Penny has to decide between auditioning for a movie or keeping her pharmaceutical sales job.
Wolowitz questions his engineering skills after he and Sheldon can't get a toy drone to fly; a canceled flight puts Leonard's plans in jeopardy; Raj sets his parents against one another after he's cut off financially.
When Sheldon's and Leonard's mothers finally meet, personalities collide; Howard decides to do his share of the chores -- with a little help from his friends.
While facing dramatic changes in his relationship with Amy, Sheldon pushes Penny and Leonard to choose a wedding date.
Penny's first date with Leonard goes awry; Penny finds Sheldon to be an unwilling confidant.
After seeing Penny with a handsome new guy, Leonard rushes into a rebound relationship with Sheldon's nemesis, Leslie Winkle.
Sheldon creates a monster when he introduces Penny to online gaming.
Raj gets an inflated ego and makes a play for Penny after being referenced in a magazine article.
Leonard and his friends stage an intervention to force Sheldon to face his fear of driving.
Sheldon and the gang are confused when a young grad student is attracted to him.
When Sheldon bans Penny from the apartment for a series of petty infractions, Penny vows to get revenge.
Leonard inadvertently steals away the new woman Wolowitz thinks is the love of his life.
Sheldon is thrilled when Leonard starts dating a woman who meets Sheldon's stringent standards.
Leonard asks Penny for advice when his new relationship starts moving too fast.
Penny starts dating Leonard's handsome colleague; Leonard and his friends are tortured by Sheldon's obsession with gift-giving etiquette.
When Penny's comment about Wolowitz's love life sends him into a depressed stupor, his friends lose their most important teammate in an upcoming fighting-robot competition.
Sheldon develops a scientific procedure for making friends; Kripke controls a new supercomputer.
Sheldon's solution to Penny's financial difficulty leads to a confrontation between Leonard and Penny's ex-boyfriend.
Leonard and Penny are drawn together after a disastrous visit from Leonard's mother (Christine Baranski).
When Sheldon tries to prove his mental superiority as they train for the Physics Bowl, the guys kick him off the team and bring his nemesis (Sara Gilbert) aboard.
Leonard and the guys buy a time machine prop from a classic movie; Penny tells the guys their obsession with comics and toys is pathetic.
Leonard devises a plan to eliminate his rivals when he, Wolowitz and Koothrappali all fall for Sheldon's twin sister, but his plan backfires when Sheldon decides to choose who his sister dates.
Penny learns that Leonard does not celebrate birthdays, so she plans a surprise party; Sheldon unexpectedly gets to live out one of his biggest fantasies in an electronics store.
When Leonard finally works up the courage to ask Penny out on a date, they each turn to Sheldon for advice.