It become traditional for girls to "slut up" whatever costume it is they choose to wear for Halloween. If you're a nurse, you're a slutty nurse. If you're a cop, you're a slutty cop. If you're a tree, you're a slutty tree.
Thing is, usually it should be pretty obvious what kind of slutty costume it is you're wearing. So what particular kind of a slut is Paris Hilton supposed to be for Halloween?
I guess she's just going as a slutty slut. Oh, wait. I know what she is. She's a slutty Paris Hilton. No, that can't be right. That's just redundant.