You need to wear a white sweatshirt and sweatpants.
Get a rope (like white clothesline rope) and a roll of toilet paper; tie it around your waist, with the toilet paper behind you.
Optional, but fun: At a novelty or costume shop, get a plastic urinal and hang it around your neck, in the front. Or, just hang more rolls of toilet paper on you.
Take some colored Sharpie markers with you and let people write all over you, like a bathroom wall.
Thanks to Sean for this creative idea!