Joe, just punch them in the face

You could switch their salt and sugar. Put icy-hot in their underwear. Eat all their food and then take a saught in their closet. Put Dish washing soap (the kind you put on a sponge to wash dishes with your hands) in their dishwasher and turn it on....bubbles everywhere! Trust me, i did it once when we ran out of dishwasher liquid. I thought that cuz their both dishwashing soaps, that they could be interchangeable, but i was very wrong.