The Grim Adventures of Billy and Mandy - -5

Billy's not just an idiot, he's an… advanced idiot. (according to IQ tests, 20 or below is "idiot")

I've theorized that, if you have a negative amount of something, that means you're counter-productive. For example, if you're $400 in debt and you don't have any money, that means you have -$400 dollars.
If you have an IQ of -10, that means that you don't solve problems. You make them harder to solve.