The US Secret Service has strict rules for making replicas of paper currency. The bills must be: either substantially larger or smaller than real ones, and blank one side. But that sometimes isn't good enough for movies and TV shows that require scenes with lots of money. So currency prop makers sometimes break the rules, and sometimes get in trouble:
In late 2000, the producers and crew for action flick Rush Hour 2 gathered at the now-defunct Desert Inn in Las Vegas and prepared to blow up a casino. The scene, which pitted policemen and Secret Service agents against a counterfeiter attempting to launder $100 million in superdollars, was to culminate with hundreds of thousands of fake bills floating through the air.
After several days of filming, the sequence was a success. Then, something incredibly odd happened. The bills, which had been supplied by a major Hollywood prop house, were picked up by movie extras and passersby and were attempted to be passed off as legal tender in various stores along the strip. The authorities weren’t too thrilled. Secret Service agents glided in, swiftly detained somewhere north of $100 million worth of prop money, then accused the prop maker -- Independent Studio Services (ISS) -- of counterfeiting, and ordered a cease and desist on all of their faux cash.