This one is easy- it's "done with mirrors"!
Everybody like money tricks! The basic effect: Show a wooden paddle with three rubber bands on it. Place a coin under one of the bands, give the coin a squeeze, shake the paddle and you've duplicated the coin! Now there is a coin on BOTH sides of the paddle!
Put another coin under another band, give a squeeze and a shake- now you have TWO coins on BOTH sides of the paddle! Repeat one more time- now you've got THREE coins on BOTH sides of the paddle!
BUT WAIT- WATCH THIS! You can actually remove ALL SIX COINS! Yes, there are really six coins!
AND THAT'S NOT ALL! After the coins are removed, give the paddle another shake- and a DOLLAR BILL is now under the bands! Remove the dollar bill- and show that ii is indeed REAL!
AND ONE MORE THING! After you remove the bill from the paddle, give it another shake. Explain "how it's done"- turn the paddle over and show that it's covered in mirrors!