This looks like trick photography but happens right before their eyes.
Have a card is selected, signed, and its lost in the deck.
A random card is removed, but isn't the chosen card.
This random card is inserted in a plastic sleeve to isolate it and avoid any chance of "tricky sleight of hand."
The card SLOWLY and VISIBLY changes to the signed selection.
You will be blown away by how amazing this looks.
The card in the gimmick will change to different cards twice!