I am working on a version of "What's Next" using a piece of cardboard and a
marking pen.

Spectator signs the card and then you draw the spots on the card.

As the trick progresses the spots appear and are actually drawn on the
cardboard.

At the end of the trick you give the spectator the card as a souvenir
ala the paper from the drawn rising card trick.

Anyone have any ideas and/or research resources for me on this concept?
I want to credit any prior ideas.

Thanks in advance.

Does this involve.... let's say..... some kind of a ....... you know.......a N@@@ W@@@@@ of some kind?
Never seen it and it may fool them if you're quick. Sounds like an idea for the Linking Ring, One Man Parade.

http://www.imperfectreality.com/