The Conjugal Conjecture
After Leonard's father, Alfred and Sheldon's mother, Mary share an evening together, everyone deals with an awkward morning the following day. Also, Penny's family arrives for the .. show full overview
The Military Miniaturization
The Air Force shows interest in the guidance system and Penny lets it slip at work that Bernadette is expecting.
The Dependence Transcendence
Sheldon can't keep up with the late nights Howard and Leonard are putting in, Raj spends the day with a pregnant Bernadette and Penny and Amy attend a faculty party.
The Cohabitation Experimentation
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.
The Hot Tub Contamination
Leonard and Penny must separate a quarreling Sheldon and Amy when their cohabitation does not go as planned, and Sheldon threatens to break off their relationship when Amy refuses to .. show full overview
The Fetal Kick Catalyst
Penny is surprised to learn she has fans of her performance in "Serial Ape-ist" when she attends Van Nuys Comic Con with Leonard. Also, Amy hosts a Sheldon-style brunch at Penny’s .. show full overview
The Veracity Elasticity
In order to continue living with Sheldon, Amy lies to him about repairs being made to her apartment and they host an "on location" episode of "Fun With Flags" in Penny’s apartment. Also, .. show full overview
The Brain Bowl Incubation
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.
The Geology Elevation
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.
The Property Division Collision
Sheldon and Leonard must divide up their possessions and remove Penny's things from 4B.
The Birthday Synchronicity
Amy's desire to have an intimate night with Sheldon on her birthday is interrupted by Bernadette going into labor.
The Holiday Summation
Sheldon and Amy visit Leonard and Penny for the first time since the holidays and share details about their terrible trip to Texas.
The Romance Recalibration
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.
The Emotion Detection Automation
Sheldon beta-tests an MIT invention after hearing it can help him read people's emotions. Also, Leonard can't hide his feelings when Penny announces her brother is coming to town, and Raj invites his ex-girlfriends over to give him dating advice.
The Locomotion Reverberation
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.
The Allowance Evaporation
Sheldon and Amy have their first fight since moving in together and Koothrappali is shocked at the realities of financial independence when he stops receiving support from his father.
The Comic-Con Conundrum
The guys' annual trip to Comic Con is in doubt when Raj can't afford to go.
The Escape Hatch Identification
Raj searches for a cheaper living arrangement.
The Collaboration Fluctuation
Leonard, Penny and Raj adjust to their new living arrangement and Sheldon takes an interest in Amy's work.
The Recollection Dissipation
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.
The Separation Agitation
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.
The Cognition Regeneration
Leonard isn’t thrilled when Penny considers taking a new job offered by her ex-boyfriend, Zack.
The Gyroscopic Collapse
After celebrating the completion of the top-secret Air Force project, Leonard, Sheldon and Howard get an unwelcome surprise; Amy receives an offer for a summer position at Princeton as a visiting researcher.
The Long Distance Dissonance
The gang is concerned when Sheldon’s former admirer, Dr. Ramona Nowitzki, resurfaces while Amy is away at Princeton.