A really skinny guy standing next to his fat ass girlfriend, thereby making them look like the number 10. Very common around science fiction conventions and Renaissance Fairs. Theorized to occur because the guy is too much of a pussy to a). break up or b). slap her ass if she takes his food.
"See those geeks in line for the Star Wars movie?"
"Who, the guy and the girl in the Jedi outfits?"
"Yeah, they're a perfect 10"