Star Trek, RFD
Did you know that a couple episodes of Star Trek: The Old Series were filmed on Mayberry RFD sets? Really. The City on the Edge of Forever and Miri were both filmed partly in Mayberry.
(Hat Tip: Gravity Lens).
Then, of course, there was the very special "Star Trek Meets the Beverly Hillbillies" episode.
Clampett: "So, Doc McCoy, what do you think of Jethro?"
McCoy: "He's dim, Jed."