When you're not even good enough to be trailer trash, but you still desperately try.
You probably live in a subway car, much the same way as trailer park trash lives in a trailer. Except, you have literally no class.
Bob is Cletus' sub-trailer trash neighbor. Rumor has it, he eats, sleeps, and cooks in his bathroom, which is a hole in the floor of the subway car he lives in. May or may not also be a methhead.