The magician writes and shows a prediction on a card case's cellophane (for example jack of spades). Immdediately afterwards, a spectator is asked to sign the back of the cellophane and to hold the card case between his/her hands. Then another spectator chooses a card that is supposed to be identical to the one the magician just wrote on the cellophane. To everyone's surprise, the card is instead the nine of hearts. The magician waves his hand over the deck of cards and reveals that his prediction has now changed to the nine of diamonds to match the chosen card. The spectator's signature is then shown to still be on the other side of the cellophane.
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