You can also pull this trick off using a grape, and IMO it can be more spectacular than the toothpick trick. Take the grape and cut it almost all the way in half so the two halves are barely attached by a piece of skin on one side. Lay it flat in the microwave so the exposed insides of the grape are facing upwards with the small amount of remaining skin holding them together. Turn microwave on. Pray it works. Does not work 9 times out of 10 (even that is optimistic) but after you fry enough grapes you will eventually get it just right and the plasmoids will fly.