Refers to someone who is being particularly surly, moody, sour or otherwise unpleasant, a.k.a., a bitch... someone you might approach in the same way as a bag of fighting cats.
A term used in Italian-American communites (particularly in the Philadelphia area and eastward) to describe a fat person. Italian-American for "fat-ass."
Hey Joey Bag o' Donuts, how 'bout you put down that cannoli and help me dump this body into the river.