Quantum Leap
Quantum Leap is an American science fiction television series, created by Donald P. Bellisario, that aired on NBC for five seasons, from March 26, 1989, to May 5, 1993. The series stars Scott Bakula as Dr. Sam Beckett, a physicist who, believing he has invented a way to travel through time, voluntarily subjects himself to an experiment that he believes will prove the validity of his controversial theories. Sam “leaps” into the fluid of spacetime and apparently disappears forever. However, it is soon revealed that Beckett's consciousness is alive and able to transfer to and inhabit the bodies of other people existing on his timeline. The artificially intelligent computer he created operates with the assumption that in order to return home, Sam must change events in the past in order to "correct" the future course of events, which have somehow been changed in an undesirable way by an unknown agent.
Plot
In the very near future, physicist Dr. Sam Beckett (Scott Bakula) theorizes that time travel within one's own lifetime is possible, and obtains government support to build project "Quantum Leap". Some years later, having already spent $43 billion, the government threatens to halt funding, as apparently no progress has been made. Sam then decides to test the project accelerator himself to save the project, telling no one. He is immediately thrown back in time, but upon awakening, finds that while he physically exists in the past, he appears to everyone else as a person into whom he has "leapt", and further has partial amnesia related to his own identity.