Where socially awkward scientists experiment with love, hilarity is sure to follow. In this season, the gang’s romantic universe expands as Leonard (Johnny Galecki), Howard (Simon Helburg), Raj (Kunal Nayyar), and even Sheldon (Jim Parsons) test their skills outside of the lab. On the rebound from Penny (Kaley Cuoco), Leonard falls into the arms of Raj’s sister, Priya (Aarti Mann). Sheldon finally gets a girlfriend -- or rather a friend who is a girl -- in Amy (Mayim Bialik), a dour neurobiologist who adopts Penny as her new best friend. The chemistry between Howard and Bernadette (Melissa Rauch) heats up -- and so do Raj and Bernadette (at least in Raj’s Bollywood daydream). The romantic twists and turns, both real or imagined, continue to bring on the laughs in this award-winning series. The Big Bang Theory: The Complete Fourth Season includes all 24 episodes of the show's 2010-11 run, along with such bonus material as "Actor on Actor: The Big Bang Theory of Relativity," in which the series' stars interview one another about working on the show, as well as a gag reel. The Blu-ray edition adds an additional featurette that goes backstage at a live taping of the show.