Magic Sponge Ding Dong.
Warning! X-Rated magic ahead! The magician displays two sponge balls at his fingertips. One of the balls is held onto by the magician and the other is placed in a spectator's hand. The magician snaps his fingers and opens his hand to show the ball has completely vanished! When the spectator opens her hand, she has two balls. Both balls are placed back into the spectator's hand and the magician again makes his ball vanish. When the spectator opens her hand, now she has three balls! The magician offers to try it again one last time. The three balls are placed into the spectator's hand who closes it into a fist. This time the magician asks, "How many balls do you think are in your hand?" No matter what her answer, she couldn't possibly guess what she's holding onto when she opens her hand-the magic ding dong!
Magic Sponge Ding Dong