Furball?
I'm assuming you mean some perjorative interpretation of that term, but I'll be damned if I know what the thing is.
Hairball, screwball, those come to mind.
But in order to be properly insulted I'm going to have to ask what "furball" is. Otherwise I'll have to assume you mean a warm, friendly guy, good-company-on-a-winter's-evening sort of thing.
Arf (maybe it refer to dog somehow. But that's warm and friendly, too. Dunno.)