They never pick up the tab. Ever.
Seriously nasty table manners.  
Bad pet sitters: "Thanks for looking after my cat. Ummm...where IS my cat?" 
Will occasionally try to eat you during sporting events.
Epic cheaters at Scrabble. For the record, "Bagnackxzll" is not a word. No, you cannot cite the Zombie Dictionary.
Never change clothes. Not big on hygiene. 
Constantly requesting "Monster Mash" from local radio station.
Forget that body parts cannot go in the blue recycling bins.
Uncomfortable in-joke gig