The Big Bang Theory is an American sitcom created by Chuck Lorre and Bill Prady, both of whom serve as executive producers on the show along with Steven Molaro. All three also serve as head writers. It premiered on CBS on September 24, 2007. On May 16, 2013 the final episode of the sixth season, The Bon Voyage Reaction aired. The season premiered on September 27, 2012. The show is centered on five characters: roommates Leonard Hofstadter and Sheldon Cooper; Penny, a waitress and aspiring actress who lives across the hall; and Leonard and Sheldon's equally geeky and socially awkward friends and co-workers, aerospace engineer Howard Wolowitz and astrophysicist Raj Koothrappali. The geekiness and intellect of the four guys is contrasted for comic effect with Penny's social skills and common sense. Over time, supporting characters have been promoted to starring roles: Leslie Winkle, a physicist colleague at Caltech and, at different times, a lover of both Leonard and Howard; Be...