When Andy first meets the woman who runs the boarding house, the beer can in her hand changes position.
Andy tells Barney his former job is still open, implying that Warren Ferguson was forgotten.
The Mayberry school pennant in Barney's apartment is green. It has been established previously in the series that the school's colors were orange and blue.
The end credits had the character names reversed for actors Peter Madsen and Charles Horvath.
Andy makes a professional gaff when he's laying his snare for Mom and the boys, telling Barney that "this gang" never hits the same place twice. Being that specific about the insider theories could've tipped them off that he knew more than he was letting on. Even Captain Dewhurst only referred to the robbers as "him".