School Story:
Back when homecoming pranks wouldn't get you arrested, I thought about taking lawn fertilizer and writing NEHI on the St. Pete Green Devil's football field in really big letters. Either the grass would get thicker and NEHI would be visible, or the grass would die and have to be replaced and NEHI would be visible. A subtle prank, but would have been funny.
But I never went through with it. Too bad.