I remember a friend pranking other friends, the quizmaster would rotate his pair of hands palm up or palm down and the victim had to guess either "opened" or "closed". Slowly the kids would get it after a few steps, frustrating the "main" victim of the prank. In the end it turned out the state was whether the quizmaster left his arms pressed against his body (closed) or a few inches "opened". A variant would be whether he'd leave his lips pressed together or slightly apart...