Episode Guide :: Season 4

• 401
  The Robotic Manipulation September 23, 2010
• 402
  The Cruciferous Vegetable Amplification September 30, 2010
• 403
  The Zazzy Substitution October 7, 2010
• 404
  The Hot Troll Deviation October 14, 2010
• 405
  The Desperation Emanation October 21, 2010
• 406
  The Irish Pub Formulation October 28, 2010
• 407
  The Apology Insufficiency November 4, 2010
• 408
  The 21-Second Excitation November 11, 2010
• 409
  The Boyfriend Complexity November 18, 2010
• 410
  The Alien Parasite Hypothesis December 9, 2010
• 411
  The Justice League Recombination December 16, 2010
• 412
  The Bus Pants Utilization January 6, 2011
• 413
  The Love Car Displacement January 20, 2011
• 414
  The Thespian Catalyst February 3, 2011
• 415
  The Benefactor Factor February 10, 2011
• 416
  The Cohabitation Formulation February 17, 2011
• 417
  The Toast Derivation February 24, 2011
• 418
  The Prestidigitation Approximation March 10, 2011
• 419
  The Zarnecki Incursion March 31, 2011
• 420
  The Herb Garden Germination April 7, 2011
• 421
  The Agreement Dissection April 28, 2011
• 422
  The Wildebeest Implementation May 5, 2011
• 423
  The Engagement Reaction May 12, 2011
• 424
  The Roommate Transmogrification May 19, 2011

Season Recap

The Big Bang Theory's fourth season focuses on character growth as Sheldon enters a platonic relationship with Amy, Howard restarts his romance with Bernadette, and Leonard starts a serious relationship with Raj's sister Priya.

As Sheldon becomes comfortable spending more time with Amy, his "girl who is a friend but not a girlfriend", starts to spend more time with the group and forms friendship with Penny. Howard's girlfriend Bernadette also becomes a part of the group. After dating for a few months, Howard and Bernadette get engaged after he proposes.

Leonard enters a long-term relationship with Priya, Raj's sister, after she moves to Pasadena. Seeing Leonard with another women, Penny begins to regret breaking up with him. In the season finale, after a night of drinking, Raj and Penny get very close.

The Big Bang Theory's fourth season contained twenty-four episodes aired between September 23, 2010 and May 19, 2011. For its fourth season, The Big Bang Theory moved to Thursdays at 8:00 on CBS, to form a new comedy block. Although the show continued to perform well in the ratings, it fell somewhat from the third season. The new timeslot lacked the strong lead-in the show had on Mondays, with TV's then-#1 sitcom Two and a Half Men, and suffered fewer people watching TV at the earlier time. Kaley Cuoco was absent from two episodes during the season, due to a broken leg from a horseback-riding accident.