The toilet was overflowing the other day, and I didn't have a plunger. Water was spilling out over the sides, so I grabbed an empty bottle to fill with water in the hope of lowering the water level in the toilet. Within a few seconds of submerging the bottle's opening in the toilet, the toilet flushed...bad-arse! It could be a coincidence, but it seems to me that the bottle filling with water caused a vacuum effect, much like a plunger, jostling the clog and allowing the toilet to flush. So if you are ever in dire need of a nonexistant plumber, try a bottle (or, really, any sort of container, I suppose).