Doll
To play this in a contest, you need a Water Neopet. When you bank this card with a Water Neopet or Hero, choose an arena. You may choose one Neopet controlled by each player in that arena, untap them and exchange control of them. (They can't be traded in or replaced.) At the end of the turn, each one goes back to its owner. (Each one stays in the arena it's in at the end of the turn.)
If you misplace your personal belongings on Mystery Island, thieves are the least of your worries!