Peeple; Urine Induced Art By Alex Schweder & Dieter Janssen

http://ifitshipitshere.blogspot.com/2010/04/peeple-urine-induced-art-by-alex.html
In the designers' words "Peeple are playthings for peetime. They are heat sensitive decals with two layers installed on the interiors of upright urinals. When heated by urine, the top layer disappears thereby revealing the characters in their underclothes."