I Need A Halloween Costume

We just received an e-mail from our HR department giving us permission to dress up on Friday. But I don't have a costume and really don't want to go buy one. I want to dress up because they area allowing us to. FREEDOM YEAH!! The costume cannot be anything that is risque or deals with political or religious statement (or may otherwise offend people)...so basically dominatrix, Sarah Palin and the Pope are out for costumes. Anyone have any good/cheap/creative ideas for a costume that I would mostly already have around my house.