There was LionCash, back in 2008, though it didn't carry much further than 4chan and a bunch of Reddit for more than a couple of years. Still, I got one before, so I'd call it a successLilani said:I wish something that epic would take the US by storm...all I really see is a bill every now and then with that "WheresGeorge.com" site or whatever, where you're supposed to register and track the bill as a sort of social experiment to see how far money travels. I don't really have anything against the idea, I'm just never too concerned about my money when I'm in a situation where I can sit down and do that.

Edit: Might as well point out that in the US, it's alright to draw on currency so long as you don't make it unusable. So be careful not to cover the serial number, signatures, etc. Otherwise, have fun.