When a man is doing a woman from behind, the woman sneakily puts on a strap on (preferably made of a tough plastic complete with coloring). As the man is about to thrust inward, the woman shifts her balance so the man falls to the bed/tabletop/elevator floor/wherever the mating is occuring, and then the woman jumps on his back as he is still utterly confused and begins to bang him relentlessly in the asshole.

when you've done something so cringe you can't stop replaying it in your head and it stops you from getting on with your every day life