Other mistake: While Sam is working in the yard, Goober drives up and hands Sam a registered letter from New York City. The post office had called Sam to tell him Goober was bringing the letter. However, a registered letter has to be signed for by the addressee. (The delivery receipt is form #3849.) Goober would not have been allowed to sign for it.
Mayberry R.F.D. (1968)
1 other mistake in The Panel Show
Starring: Ken Berry, George Lindsey, Jack Dodson, Paul Hartman
Aunt Bee's Cruise: Part 2 - S1-E16
Factual error: Captain Wolford tells Aunt Bee that he has performed several shipboard weddings. Contrary to popular belief, sea captains have no authority to perform weddings.