Season 4
This season the Big Bang gang’s romantic universe expands. On the rebound from Penny, Leonard falls into the arms of Raj’s sister Priya. Sheldon gets a girlfriend, or rather a friend who is a girl: Amy, a dour neurobiologist who declares herself besties with Penny. Howard and Bernadette heat up. And so do Raj and Bernadette (at least in Raj’s Bollywood daydream).
Episodes
1 The Robotic Manipulation Sep 23, 2010 
2 The Cruciferous Vegetable Amplification Sep 30, 2010 
3 The Zazzy Substitution Oct 7, 2010 
4 The Hot Troll Deviation Oct 14, 2010 
5 The Desperation Emanation Oct 21, 2010 
6 The Irish Pub Formulation Oct 28, 2010 
7 The Apology Insufficiency Nov 4, 2010 
8 The 21-Second Excitation Nov 11, 2010 
9 The Boyfriend Complexity Nov 18, 2010 
10 The Alien Parasite Hypothesis Dec 9, 2010 
11 The Justice League Recombination Dec 16, 2010 
12 The Bus Pants Utilization Jan 6, 2011 
13 The Love Car Displacement Jan 20, 2011 
14 The Thespian Catalyst Feb 3, 2011 
15 The Benefactor Factor Feb 10, 2011 
16 The Cohabitation Formulation Feb 17, 2011 
17 The Toast Derivation Feb 24, 2011 
18 The Prestidigitation Approximation Mar 10, 2011 
19 The Zarnecki Incursion Mar 31, 2011 
20 The Herb Garden Germination Apr 7, 2011 
21 The Agreement Dissection Apr 28, 2011 
22 The Wildebeest Implementation May 5, 2011 
23 The Engagement Reaction May 12, 2011 
24 The Roommate Transmogrification May 19, 2011