Barn's trying to create havoc as you know so Andy won't move away.
The scene, in front of the Courthouse, looks like it's shot on a sound stage. Goober's in his truck, Otis is in a car(!) facing opposite direction ready to spread the havoc evenly around town, I guess - Barney standing in-between them, and falls as they speed away.
Goober says disappointingly something like, 'Ah, aren't you gonna let us rob a bank?'.
Great line for George Lindsey.