I was just at Old Navy last night and they have some kit-things you can buy that have things like mouse ears and a tail... I don't think they were very much but I didn't look.

Once, for a Beatle-fan's birthday party, we were supposed to come dressed as our favorite Beatles song. I made a LIFE cereal box to go over my head, with a cutout for my face. Don't know what happened to the box, it's probably somewhere in my basement or something...

Remember, you can never go wrong with the Groucho nose & moustache. ;-)