Get two different color PEEP candies (blue and yellow or whatever they have), one plate, and a microwave oven. Put the two PEEPs onto the plate in the Microwave.

Turn it on high and see which PEEP pushes the other off the plate as their marshmallow selves expand. Be sure to turn of the microwave before it REALLY gets messy !

We'll be doing this one shortly at our gathering time for youth fellowship!

(YWM suggested addition: Try setting up a camera and a larger screen so that all the youth can see the Sumo Action!)