The social situation on The Big Bang Theory undergoes a little change in season four.  Leonard (played by Johnny Galecki) begins to get over being dumped by Penny (played by Kaley Cuoco) and finds a new girlfriend, Sheldon (played by Jim Parsons) has a friend who is a girl, Penny has a new best friend, and Howard (played by Simon Helberg) and Bernadette (played by Melissa Rauch) get serious.  It’s all genius, laughs and social awkwardness.

Episode 1: The Robotic Manipulation: Penny helps Sheldon on his first date with Amy (played by Mayim Bialik).

Episode 2: The Cruciferous Vegetable Amplification: Sheldon goes on a healthy eating and safety first kick after her realizes that the technology to download his knowledge into a robot will not be ready before he dies.

Episode 3: The Zazzy Substitution: The guys think Sheldon is replacing Amy with cats after the breakup.

Episode 4: The Hot Troll Deviation: Howard tries to get back together with Bernadette.

Episode 5: The Desperation Emanation: Amy wants Sheldon to meet her mother.

Episode 6: The Irish Pub Formulation: Raj’s (played by Kunal Nayyar) sister (played by Aarti Mann) is in for one day on a layover and he forbids any of the guys from hooking up with her.

Episode 7: The Apology Insufficiency: Howard needs security clearance from the FBI so the guys all have to be interviewed, including Sheldon.

Episode 8: The 21 – Second Excitation: The guys camp out to see a version of Raiders of the Lost Ark with 21 never-before-seen seconds and are irate when Wil Wheaton and friends are allowed to skip the line.

Episode 9: The Boyfriend Complexity: While Penny’s father is visiting she asks Leonard to pretend to still be her boyfriend.

Episode 10: The Alien Parasite Hypothesis: Raj and Howard argue over who would make the better superhero.

Episode 11: The Justice League Recombination: The guys convince Zack (played by Brian Smith) and Penny to join them at a comic book store New Year’s Eve party and wear Justice League costumes.

Episode 12: The Bus Pants Utilization: Leonard and Sheldon friendship becomes strained when Sheldon takes over the developing of an app that Leonard is working on.

Episode 13: The Love Car Displacement: Bernadette runs into an ex at a science convention leading to Howard feeling inadequate.

Episode 14: The Thespian Catalyst: Raj has fantasies starring Bernadette.

Episode 15: The Benefactor Factor: Leonard ponders whether he would have sex again with an older but wealthy donor in order to secure another donation.

Episode 16:  The Cohabitation Formulation: Raj’s sister Priya is back in town and Leonard attempts to rekindle their romance which upsets Penny.

Episode 17: The Toast Derivation: After being told that Leonard is the center of the group, Sheldon attempts to form another group of friends in which he is the center.

Episode 18: The Prestidigitation Approximation: Priya does not approve of Leonard remaining friends with Penny.

Episode 19: The Zarnecki Incursion: Bernadette and Amy try to console Penny over Leonard and Priya’s relationship.

Episode 20: The Herb Garden Germination: Howard and Bernadette’s relationship is taken to the next level.

Episode 21: The Agreement Dissection: Priya rips apart the Roommate Agreement using legal theory much to Sheldon’s chagrin.

Episode 22: The Wildebeest Implementation: Sheldon develops three-person chess.

Episode 23: The Engagement Reaction: Howard’s mother has to be admitted to the hospital after he tells her he is marrying Bernadette.

Episode 24: The Roommate Transmogrification: Raj moves in with Sheldon after he hear his sister and Leonard playing Star Trek sex games.

Special Features:  Actor on Actor: The Big Bang’s Theory of Relativity, The Bare Naked Ladies on Big Band Theory, The History of Everything Music Video, Gag Reel