We should be talking about Quantum Leap so much more than we are. It was a great show, and every now and again it had episodes so good and weird that they're all-timers. Like the time Dr. Sam Beckett leapt into the body of a boy with Down Syndrome. Or the time he was getting shock treatment in a mental asylum that mixed up his brain. Or the time he accidentally gave young Stephen King the ideas for most of his novels. And then there's the series finale, which is one of the most amazing finales of all time and does not end with Sam leaping home - in fact it's said that he never gets home. It's heavy stuff.
But one of the best episodes of Quantum Leap also had the best twist ending in the series' history, an ending that really played with the show's whole concept. See, Sam Beckett was leaping from body to body and setting right things that went wrong; he was basically fixing the future from which he came (1999 in the show's chronology). But it was almost always small stuff, little ripples in the big pond of time. By season five the network wanted Sam to interact more with historical figures (the Stephen King episode is a good example of the ways he usually met famous people - glancingly and ironically) and so showrunner Donald P. Bellisario opened that year by placing Sam right in one of the biggest events in American history: the Kennedy assassination.
Over the course of a two-parter Sam leapt in and out of different parts of Lee Harvey Oswald's life. Sam assumed that he was there to stop Oswald from killing Kennedy, or to get to the bottom of the conspiracy, but all of that gets complicated when Sam and Oswald start merging together. Usually when Sam leaps into someone they end up in his body in the future, but this time something has gone terribly wrong, and Sam battles for control of Oswald's body. As the show goes on Al desperately tries to get Sam out of the body before he, believing he is Oswald, pulls the trigger and kills Kennedy.
At the last second Sam leaps out of Oswald, but he's not out of Dallas on November 22nd. He immediately leaps into the body of Secret Service agent Clint Hill, who was in the motorcade and jumped onto the back of the Kennedy limo as the president was shot. Sam is depressed, thinking that he has failed at his mission and he's allowed Kennedy to be killed, but then Al shows up and delivers the whopping twist: in the original timeline Jackie died as well. Sam saved her life, and that was the purpose of the leap.
The episode is unique in Kennedy assassination media in that it unequivocally comes down behind Oswald as the lone shooter. There is no conspiracy, and Al even talks about why we like the conspiracy theory so much, because it's comforting to believe that it takes a group of powerful men to disrupt the world as opposed to one psychotic loner. That point of view was very personal for Bellisario, who actually had met Lee Harvey Oswald while they both served in the Marines. In fact, there's a Sgt. Bellisario who makes a cameo in the first part of the two-parter.
You can watch the Lee Harvey Oswald episode of Quantum Leap above... if you're a Hulu Plus subscriber.