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!"