Quantum Leap is an American television series that was broadcast on NBC from March 26, 1989 to May 5, 1993, for a total of five seasons. The series was created by Donald P. Bellisario, and starred Scott Bakula as Dr. Sam Beckett, a quantum physicist from the near future who becomes lost in time following a time travel experiment, temporarily taking the places of other people to "put right what once went wrong". Dean Stockwell co-starred as Al Calavicci, Sam's womanizing, cigar-smoking sidekick and best friend, who appeared as a hologram that only Sam, animals, young children, and the mentally ill could see and hear. The series featured a mix of humor, drama and melodrama, social commentary, nostalgia, and science fiction, which won it a broad range of fans. One of its trademarks is that at the end of each episode, Sam "leaps" into the setting for the next episode, usually uttering a dismayed "Oh, boy!" Despite struggling on Friday nights in its brief first season, the show was renewed by NBC because of its impressive 18-49 demographics. The series was moved to Wednesdays where it performed well in comparison to other fan-favorite series Wiseguy and China Beach. It was moved twice away from Wednesdays to Fridays in late 1990 and to Tuesdays in late 1992 where it also performed well. The series finale aired in its successful Wednesday slot in May 1993.