Watch The Big Bang Theory series free. The Big Bang Theory is an American sitcom that stars Johnny Galecki, Jim Parsons, Kaley Cuoco, Simon Helberg, Kunal Nayyar, Sara Gilbert, Melissa Rauch and Mayim Bialik. The show surround with 5 characters: 2 roommate geniuses who work at the California Institute of Technology, experimental physicist Leonard Hofstadter and theoretical physicist Sheldon Cooper; their neighbor across the hall Penny, a blonde waitress and aspiring actress; and Leonard and Sheldon's equally geeky and socially awkward co-workers and friends Howard Wolowitz, an aerospace engineer and a non-PhD from JPL, and Rajesh Koothrappali, an astrophysicist also working at Caltech.
