Two different people select cards, and these are mixed into a regular poker-sized deck. The deck is given to someone to hold between their hands. The magician reaches into the deck that's between their palms and miraculously retrieves both selections. He then states that he will take the whole deck from them without anyone knowing. The spectator clamps down tight on the deck to prevent this. The magician shows that he has the deck by producing one from his pocket. The audience is in disbelief. The magician then says, "What if I told you that you didn't have any cards? What if I told you it was a creature, something poisonous that most people are afraid of?"
This piques their interest. When they open their hands to find a clear block with a scorpion inside, everyone freaks out!! This gets HUGE reactions. The creature inside is real -- inanimate but real. This gives most people the heebie-jeebies.
This does not include cards. Any poker-sized deck can be used.