My friend and I did a conjoined twin ghost one year - we'd committed mutual suicide because we'd fallen in love with the same man. Isn't very condusive to walking around on your own, though!
I saw a picture of a couple once - the guy was dressed as a salesman (suit, fedora, briefcase) and the woman was dressed as the Grim Reaper. They were "Death and a Salesman".
I like your trick or treat idea, though!
