One of the most desired things that people imagine doing if time travel were possible, aside from killing Adolf Hitler, is saving President John F. Kennedy. At least two television series imagine how that might have taken place.
Some spoilers may follow.
In the 1980s version of “The Twilight Zone” in an episode called “Profile in Silver” a professor of history at Harvard in the 22nd Century named John Fitzgerald, a direct descendant of the murdered president, gets the opportunity to go back in time to Dallas on November 22, 1963 to observe directly the assassination. Not being able to stand seeing his famous ancestor killed in front of his eyes, Professor Fitzgerald shouts a warning, causing the president and his party to take cover and Oswald to miss.
Unfortunately this alteration of history causes a rip in the time/space continuum that threatens to destroy the universe. Fitzgerald decides to rectify the situation by having Kennedy transported to the future and himself transported to the open limo on the fateful day, dying in the place of the president. Agents from the future cover up the substitution and Kennedy assumes his place as a history professor at Harvard in the 22nd Century.
The other notable saving Kennedy episode took place in the TV series “Quantum Leap.” The series depicted the adventures of a scientist named Sam Beckett who is sent back and forth in time to occupy the bodies of people in the past and change history, usually the personal lives. In a two part episode “Lee Harvey Oswald” Beckett finds himself leaping back and forth into the body of Lee Harvey Oswald, the assassin of President Kennedy.
As a side note, the show’s creator, Donald Bellisario actually served in the Marine Corps in the late 1950s with Oswald and he appears as a character in the two part TV episode.
Beckett has to deal with Oswald taking over his will even as he and his controller back in the present, Al, struggle to find a way to save President Kennedy. However, as it turns out, the mission is not to save the president at all. After Beckett is transferred into the body of a Secret Service Agent on that fateful day in Dallas, shouting a warning, it is revealed that in the original timeline Jacqueline Kennedy also died and his mission was to save her life.