Excellent trick to be done with the proper audience.
I like to present it as an accidental
transpo with a condom.
1. A card is chosen and disappears from the deck.
2. The magi
announces it will reappear in the card box
3. When he opens the card box, a condom appears
instead
4. The magi looks surprised, but explains it's probably due to a transpo between the
card and condom.
5. He then changes the card into a wrapped condom that he gives to spectator to
be opened.
This gives a good justification, IMHO, to the bizarre and sudden transformation
of the card into the wrapped condom.
Nota Bene : I found that the condom is hard to unwrap
in the end, because the condom enveloppe is very hard to tear.
This is a good point as it builds
the suspense.
But that said, it might be a good idea for the magi to make a slight slit at the
side of the wrapping before the trick, to facilitate the tearing.
Or to hold a tiny pair of
scissors during performance, just in case nobody can tear the condom enveloppe.