In the original Star Trek episode "City on the Edge of Forever" (aired April 6, 1967), Jim Kirk travels back in time to Depression-era New York to stop a drugged-out McCoy from somehow changing history.
He meets social worker Edith Keeler, falls in love with her, then finds out he has to allow her to get run over by a truck to preserve history.
It's a superb episode, despite some arguably unnecessary changes from Harlan Ellison's original script. But aside from being excellent drama and intelligent science fiction, the episode also establishes that Star Trek and The Andy Griffith Show share the same reality.
Take a look at the photo above. Kirk and Edith are walking by Floyd's Barber Shop, a staple business in Mayberry.
But this episode takes place in New York, not Mayberry. So what's the explanation?
Well, it's all very simple: