Seeing Gomer and Barney standing in front of the Mayberry Security Bank brings back memories about one of the times Barney deputizes Gomer ("Andy's Vacation," Episode #118). Gomer is a little green, but still the cream of the crop, according to Barney.
Barney shows Gomer everything he needs to know about law enforcement. That means double trouble for Mayberry, and very little time for Andy to relax and read his National Geographics while on vacation.