One who is an Assmouse wearing Cheesepants. Or one who is the "wanna be" of the group, and is always bugging you for a nickname. Assmouse Cheesepants is the perfect solution for such a friend.
Jon: C'mon guys give me a nick name!
Ken: Dude just shut up.
Larry: Ok fine Jon. You're now Assmouse Cheesepants.