The magician displays two jokers and places them on the table. Next, a spectator is asked to select a card and sign it across the face. The card is then returned to the deck. The Jokers are picked up from the table, and one card is trapped between them-but it is the wrong card. Magically and visually, the wrong card changes into the spectator's signed selection! Of course the spectator may keep their card as a souvenir.
This effect will hit them like the proverbial freight train! Strong, simple, and visual magic.