The Proton Resurgence
Season 9, Ep. 22
Leonard and Sheldon hire the host (Bob Newhart) of their favorite childhood TV show to perform; Bernadette and Howard run into trouble while dog-sitting for Raj's pet.
Read more: Sheldon meets his childhood idol on ‘Big Bang Theory’ but ends up riding with him to the hospital
First Aired: May 2, 2013
The Closure Alternative
Season 6, Ep. 21
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.
First Aired: April 25, 2013
The Tenure Turbulence
Season 6, Ep. 20
The girls get involved when Leonard, Sheldon and Raj compete for tenure at the University.
First Aired: April 4, 2013
The Closet Reconfiguration
Season 6, Ep. 19
Howard considers whether or not he should open a letter from his father; Penny and Leonard host a "grown-up" cocktail party.
Read more: You’re invited to a 'Big Bang Theory' dinner party
Read even more: Cast celebrates success of past 4 years, but withholds spoilers
First Aired: March 14, 2013
The Contractual Obligation Implementation
Season 6, Ep. 18
Leonard, Sheldon and Wolowitz talk to junior high girls about science-related careers; Raj plans a date with Lucy.
Read more: The guys head back to junior high, while Raj tries to sweep Lucy off her feet
Gallery: Forget the lab or the couch, the cast of 'BBT' hits the red carpet
First aired on March 7, 2013.
The Monster Isolation
Season 6, Ep. 17
Raj is put out when his date walks out in the middle of their evening, so he vows that he will forever stay put in his apartment. Meanwhile, Sheldon is quite impressed when he witnesses Penny's acting skills firsthand.
Read more: Love was in the air...but maybe not for Raj
First aired on February 21, 2013.
The Cooper/Kripke Inversion
Season 6, Ep. 14
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.
Read: My 88-year-old 'Meemaw's' love of 'Big Bang Theory'
First aired on January 31, 2013.
The Bakersfield Expedition
Season 6, Ep. 13
As the guys don costumes and go on a road trip to a comic book convention, the ladies decide to stay home and try to interpret a comic book.
First aired on January 10, 2013
The Egg Salad Equivalency
Season 6, Ep. 12
When Sheldon is accused of sexual harassment, he ends up getting Raj, Leonard and Wolowitz in trouble.
First aired on January 3, 2013.
The Santa Simulation
Season 6, Ep. 11
Sheldon has issues with Santa Claus on Christmas.
First aired on December 13, 2012.
The Fish Guts Displacement
Season 6, Ep. 10
Amy takes ill and Sheldon becomes her nursemaid, while Wolowitz takes a fishing trip in order to bond with his father-in-law.
First aired December 5, 2012.
The Parking Spot Escalation
Season 6, Ep. 9
Sheldon and Wolowitz's fight over a parking spot at the university impacts the whole gang.
First aired on November 29, 2012.
The 43 Peculiarity
Season 6, Ep. 8
Raj and Howard try to figure out why Sheldon disappears at 2:45 every afternoon; jealousy arises in Penny and Leonard's relationship.
First aired on November 15, 2012.
The Habitation Configuration
Season 6, Ep. 7
Bernadette wants Wolowitz to move out of his mom's house; Sheldon is caught in the middle of Amy and Wil Wheaton's argument.
First aired on November 8, 2012.
The Extract Obliteration
Season 6, Ep. 6
A game threatens Sheldon's relationship with Stephen Hawking; Penny secretly signs up for a college class.
First aired on November 1, 2012.
The Holographic Excitation
Season 6, Ep. 5
The gang heads to Stuart's comic book store to celebrate Halloween; Leonard uses science to seduce Penny.
First aired on October 25, 2012.
The Re-Entry Minimization
Season 6, Ep. 4
Wolowitz's return from space isn't all he expected; game night becomes a gender war.
First aired on October 18, 2012.
The Higgs Boson Observation
Season 6, Ep. 3
Amy feels threatened by Sheldon's new assistant; Wolowitz starts to feel the pressures of being in space
First aired on Oct. 11.
The Decoupling Fluctuation
Season 6, Ep. 2
Sheldon tries to intervene when he learns that Penny is thinking about breaking up with Leonard; Howard is picked on.
First aired on Oct. 4.
The Date Night Variable
Season 6, Ep. 1
Raj faces his loneliness when his friends are out on dates; while in space, Wolowitz gets drawn into a fight between Bernadette and his mom.
First aired on Sept. 27.
The Countdown Reflection
Season 5, Ep. 24
In the season finale, Howard and Bernadette decide to get married before his NASA mission, causing the gang to scurry into overdrive in an effort to stage the wedding.
Original Air Date: May 10, 2012
The Launch Acceleration
Season 5, Ep. 23
NASA reschedules Howard's mission, putting the wedding plans in jeopardy. Meanwhile, Leonard says something surprising to Penny in the bedroom.
Original Air Date: May 3, 2012
The Stag Convergence
Season 5, Ep. 22
Bernadette has second thoughts about marrying Howard when details of his sexual history emerge at his bachelor party.
Original Air Date: April 26, 2012