Picture of Retail April Fools Prank
If you work retail yo most likely have a counterfeit detector pen lying around the register. This trick prays on people's insecurity about money so only do this to regular customers with a good sense of humor, I cannot be held responsible for you getting you butt handed to you. The way this works is when you mark a counterfeit bill with the pen the mark turns black otherwise it will be light brown or yellow. You have to make the mark come out black.

*Edit* This may or may not work outside the US. I'm am not certain on how to detect counterfeits elsewhere but the concept is simple and could be molded to your area most likely.

Step 1: Material Needed

Picture of Material Needed
Aquire a counterfeit detector pen, a black sharpie (the closer resembling to the pen the better) and choose your victim. I have done this with everything from a $1 bill to a $100 bill and people will believe it, just find someone with a good sense of humor like I said before.
bauerbach1 year ago
If you play this on a cop, you may get arrested for counterfeiting.
puzka4 years ago
Wow. I had no idea you had counterfeit detector pens in the US. Seems a bit 20th century :-) Wouldn't the bad guys just get a pen to check their counterfeits until they got it right? Or is the pen itself a joke ;-)
Scatmanbrandt (author)  puzka4 years ago
I know, I've been thinking of buying a uv detector for my store but it would probably never get used. I never trust the pens myself due to all the false readings and normally just check it by sight.
I dunno still sounds weird. Australian money is almost impossible to counterfeit.
Scatmanbrandt (author)  puzka4 years ago
That's what I've heard, it's easier to get your teeth pulled out by a donkey then use cash there.