Invert this half rubber ball and drop it. It will bounce up higher than the release point.
Discuss conservation of energy with your students as the shape of the Dropper Popper allows it to store elastic potential energy that can be converted to kinetic energy.
There is a minium height required to trigger the popper that can be related to barrier potentials.
You can even make this a quantitative investigation by using PASCO Capstone's Video Analysis capabilities to track the Dropper Popper's path and measure it's peak height.