Okay, you wild and wacky pranksters, I present one recipe for toilet humour;
One bottle of generic blue food coloring...
One small coin in your favorite denomination...
One run of the mill folk festival/ren fest/outdoor event porta potty.
Enter the box...
Apply food coloring liberally to one arm, shoulder, and coin...
Bang around for a few minutes, cursing, muttering, bellowing, and add a few EWWWWWWWS, YUCKS, and OUCHES thrown in for flavor.
When you've gathered a curious crowd, emerge from the loo coin held high in triumph. A proud exclamation tossed in right here goes a long way..."FINALLY GOT YOU BACK YOU BASTARD...HAH!!!"
You'll be amazed how quickly word of your deed travels the event grounds.
The few times that I've (ahem) seen this done is usually well worth the effort.

Chip2447(who has pulled the plastic wrap twixt the bowl and the seat trick. Wonders why he's single and women dont have a sense of humour)
DEFECATE, OR EVACUATE THE FECAL COLLECTION RECEPTICLE