The Business of Fake Hollywood Money
There seem to be a lot of possibilities that would do in various positions.<p>If you could make the money feel distinctively different, while appearing the same, it would probably be enough to cause a receiver to pay sufficient attention to notice the minor differences.<p>Printing different denominations on each side of the bill would be sufficient for most stationary money.<p>For scenes with large amounts of free flowing money,  you could print the notes backwards and flip the film.<p>I don't think there would be any single solution for all instances, but I think you could pick a form that would suit whichever scene you were currently shooting.