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). All in the furtherance of award-winning genius comedy.

Originally aired on television in 2010-2011. Special features: Actor on actor featurette; The Barenaked Ladies on Big Bang Theory featurette; The history of everything music video; gag reel.

The robotic manipulation -- The cruciferous vegetable amplification -- The zazzy substitution -- The hot troll deviation -- The desperation emanation -- The Irish pub formulation -- The apology insufficiency -- The 21-second excitation -- The boyfriend complexity -- The alien parasite hypothesis -- The Justice League recombination -- The bus pants utilization -- The love car displacement -- The thespian catalyst -- The benefactor factor -- The cohabitation formulation -- The toast derivation -- The prestidigitation approximation -- The Zarnecki incursion -- The herb garden germination -- The agreement dissection -- The wildebeest implementation -- The engagement reaction -- The roommate transmogrification.