Costume Closet

I've been out to get a Halloween costume for a while, but I have a party on Wednesday, and I'm totally unprepared, and broke - but I want to be something really witty that does not require much preparation. I also thought that I could print an image from your computer and make a mask, but I do not know.
What are your suggestions for a Halloween costume, when really all you have is a firm of clothing?

You could be a person homeless. Take the pictures that are torn (if you have one) and rub a little dirt on them and on your face and arms. Fast and cheap.