As Security for the Hell Hole, we got a twenty that was perfect in every detail... on the front.
On the back it looked like whoever printed it dragged it across the ground or something because it was all smeared.
Guy was a Mexican, (Legal, I must add, had a green card...) and said it was what his manager had paid him with.
Called the cops, called the Treasury Department.
Turns out the guy had another bill, absolutely identical to the first. I guess whoever was making these bills had a printer malfunction because even the back was smeared in exactly the same way...
The real kicker, and what made the cashier really look at the bill... whoever printed it did so on what felt like Construction Paper, making it painfully obvious to the touch that it wasn't real...