My friend just did this trick to me, and i am stumped.
The $5 was his and the $1 was mine. He folded both and put them in my hand, pulled out the $1, still folded, shook it around. It turned into a $5 and then he showed me the $1 back in my hand.
All i know is that i felt that he took the $5 initially. So WTF?
This is a video.
http://www.magical-tricks.com/BillTransposition.wmv