Just the clothes on your back
This a great game to play with a group. My daughter plays it at her preschool and it always gets everyone laughing, adults too! Have everyone sit in a circle. One person is chosen to leave the room (they'll need an adult to help). That person then changes as much as they can about their appearance - the zanier you make it the better. Untuck their shirt or turn it inside out, tie their sweater around their leg, put a sock on their hand, put a little girl's hair in a crazy-looking ponytail, etc. They then re-enter the room and stand in the middle of the circle while the rest of the group takes turns guessing what's different. When everything has been guessed, it's another child's turn.