Trivia: This is the last episode where we see a mobile Floyd. The actor suffered a stroke. He returned to the show but is hereafter seen sitting or leaning against a wall.
Trivia: When Andy, Barney, the mayor, and Upchurch are at the courthouse with the plaster castings of the footprints, Upchurch has named the sets of prints "Able, Baker, and Charlie." The names "Able and Baker" are also the names of the two monkeys who were launched into space on May 28, 1959 in a Jupiter rocket.
Answer: It was a joke. They were supposed to be dumb hillbillies.
Both. According to later interviews with both Andy and the Dillards band (the real name of the band that played the parts of the Darling children, of which Charlene (Maggie Peterson - Mancuso was also a member) the reason the Darling boys never had any lines was because they would've had to have been paid if they spoke. In return for appearing without lines or pay, Andy promised to get as much of their music onto the show as possible which, he did. This obviously gave them a lot of exposure.