Hmm, most of the nicknames we give people are in Dutch so you wouldn't really understand them. :p well, maybe, with a little German ^_^. We call this one girl, who is really small and looks like she is 15 or so (she's really 24) "Reus" (Riese), which is "Giant". That's not all that innovative. And my cat, who is also very small, but will eat anything and everything and is ALWAYS hungry, I call her "Kleine Stofzuiger" (Kleine Staubsauger), which is "Little Vacuumcleaner".
But they're both not really mean or anything.
