Scatology has always provided fertile ground for pranks and humor. In fact, I've read scientific speculation that farts and feces probably provided the inspiration for the very first jokes told (or staged) by our early hominid ancestors. Witness how modern-day chimpanzees find it endlessly amusing to fling their feces.
This might provide us with some context for the prank called Poop Dollaring. (Though it's probably more analysis than the prank deserves.) Its method is simple: smear feces on a dollar bill and then place it so as to "tantalize the gullible".
Back when people used pay-phones, a variant of the prank involved stuffing dog poop into the coin return box. Unfortunately I remember falling victim to this once as a teenager. It was disgusting.
Knowing about poop dollaring might, if nothing else, spare you from too readily picking up some money you see lying on the ground.
Of course, youtube provides us with quite a few examples of innocent victims getting poop dollared.