One of my students brought in a little device to share with the class made of two old plastic cards, sticky tape and a single rubber band. When stretched open, folded over and released it snapped and jumped into the air. We dubbed it the Card Clapper. Another student happened to also bring in a solar powered fan cap.
This had direct relevance to our Central Idea, Energy comes from many sources, exists in different forms, is changed, stored and used in different ways. I immediately took a picture on my iPhone and posted it on our class Weebly website posing, “How does it work?” as optional homework.