Discard the joker cards from each deck. Take one deck and glue the cards face to face, creating half a deck of double-sided cards.
Discard half of the other deck, then put the half-deck of regular cards on top of the half-deck of double-sided cards to form one deck of cards.
Show the cards to the audience, then split the deck in half and lay the regular cards face-up on the table. Fan out the regular cards and ask an audience member to choose one of the cards. Have them take that card from the deck.
Shuffle all of the cards together, leaving the regular cards face-up so that the audience thinks half of the deck is face-up and half is face-down.
Fan the cards out on the table and have the audience member replace their card face-down anywhere in the deck they would like.
Shuffle the cards and flip them before fanning them out on the table once again. The card the audience member chose will be the only card that is face-up.