Halloween Extra

As a lazy but ardent fan of Halloween, I am always looking for costumes that allow me to participate in the holiday without the tedious process of buying, making, or actually dressing up in anything. I thought I might help some like-minded individuals with a list of things you can tell people you're dressed up as without actually having to change anything about your wardrobe.

The (always popular) Psychotic Killer
Infectious [Insert Nasty Virus Here] Carrier
Android
Werewolf (only works during the day, or non-full-moon evenings)
Clone (or Evil Twin)
Cannibal
Sports Fan
Undercover Cop
Eukaryote (Ah! I knew I took AP Biology for some reason...)
Soylent Green
Hallucination

Also, if you happen to have dandruff, acne, or some other non-fatal skin disease, you might be able to get away with:
Zombie
Plague Victim
Leper

The list could go on, I'm sure. Feel free to comment with your own suggestions.