Besides sticking something metal or foil in there. This is a new one. I'm betting no one thought of it before.
So what's this new way of almost destroying a perfectly good microwave? A hand warmer. One of those little bitty packs you just shake and then it heats up. Someone around here wanted a hand warmer during our cold, blustery wind storm yesterday, so they assumed it needed a spin in the zapper to heat it up.
It worked all right. The good news is that by some miracle our microwave still works.
Don't try this at home.