Part of the effectiveness of this gag is because the deck of cards appears completely standard and unopened, therefore it's surprising to have it react to being tossed or dropped and to hear sounds coming from within it!
To pull this off we need to get into the deck without ruining the cellophane or the seal on the box. We'll also need to match the feel of the deck -- it should weigh and feel the same as normal cards. Finally, we must re-seal the box and cellophane.
To unseal the deck we'll first use a small knife or thin piece of metal such as a feeler gauge to slide open the folded cellophane at the bottom of the deck. Go slowly to avoid tearing the thin plastic -- you want to pry and lift more than cut.
Next, carefully slice through the glue that holds the bottom flap of the cardboard box. Avoid bending the cardboard -- a sure sign of tampering!
Remove the existing cards and set them aside. You'll save a few to place back in the box in order to fill out the thickness properly, the rest you can potentially use in setting up a different puzzle.
Next, we'll set up the electronics by programming the Circuit Playground.