Yea, Oscar's reason for being a grouch was that he lived in a trash can, but what's his/her real reason for being intentionally unpleasant? Rejection isn't physically painful the way that being tortured is, so that's not a real reason.
Person who sits on the couch all day watching TV and barking orders at any who come within hearing distance. Also complains loudly about their lot in life even though they don't have anything to do other than sit around and watch TV.