Sorry, but you are hereby ejected from the southern naming convention panel.
As all right thinking individuals know, a critter is any non human that moves under its own power or surprises us by being alive but looking like it shouldn't be because it doesn't move under its own power, like yankees and coral.
A varmint is a critter you don't want in your garden, on your farm, and may be shot on sight, like coyote, raccoons, or yankees.
Edit: you may also substitute the following corollary to the definition of critter: any living thing which Ellie May Clampett would be likely to adopt.
