Episode Guide :: Season 4
|#||Episode||Original Air Date||User Rating|
|401||The Robotic Manipulation||September 23, 2010||4.6|
|402||The Cruciferous Vegetable Amplification||September 30, 2010||4.5|
|403||The Zazzy Substitution||October 7, 2010||4.6|
|404||The Hot Troll Deviation||October 14, 2010||4.3|
|405||The Desperation Emanation||October 21, 2010||4.2|
|406||The Irish Pub Formulation||October 28, 2010||4.3|
|407||The Apology Insufficiency||November 4, 2010||4.4|
|408||The 21-Second Excitation||November 11, 2010||4.6|
|409||The Boyfriend Complexity||November 18, 2010||4.6|
|410||The Alien Parasite Hypothesis||December 9, 2010||4.2|
|411||The Justice League Recombination||December 16, 2010||4.7|
|412||The Bus Pants Utilization||January 6, 2011||4.2|
|413||The Love Car Displacement||January 20, 2011||4.4|
|414||The Thespian Catalyst||February 3, 2011||4.1|
|415||The Benefactor Factor||February 10, 2011||4.3|
|416||The Cohabitation Formulation||February 17, 2011||4.4|
|417||The Toast Derivation||February 24, 2011||4.6|
|418||The Prestidigitation Approximation||March 10, 2011||4.6|
|419||The Zarnecki Incursion||March 31, 2011||4.8|
|420||The Herb Garden Germination||April 7, 2011||4.7|
|421||The Agreement Dissection||April 28, 2011||4.5|
|422||The Wildebeest Implementation||May 5, 2011||4.3|
|423||The Engagement Reaction||May 12, 2011||4.4|
|424||The Roommate Transmogrification||May 19, 2011||4.6|
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.