Dancing Popcorn

Prepare half glass of water with a teaspoon of baking soda and popcorn kernels.
Set it up with the elf next to it and a note saying "Want to see dancing popcorn? Pour the magic water"
Prepare a separate pouring cup with white vinegar in it and out the note against it.
When the magic water (vinegar) is poured it reacts with the baking soda and the popcorn move in the water.