Heres a trick i recently came up with, still working on it.
A spec. picks a card, writes their name on the top half of it (ace of spades for example)
Another spec. picks a differant card and writes their name on the bottom half of it (7 of hearts)
you them the 2 cards with both signatures on it (everything is perfectly normal..literally)
then with a little shake, both cards combine, half the ace is connected to half of the 7, and both signatures on it,
what you think?