My boys loved squashing them flat on the floor and watching them pop up. They actually had races to see whose would pop first!
I was originally only going to get one of these for my eldest son, until his brother saw me ordering and got upset that wasn't getting one, so I relented and ordered him one as well. The intention was to use this as a way to distract my eldest when he told to cool off in his room, when he is anxious or bored. It was put to use about a hour or so after arrival and had the desired effect of helping him calm down. His brother may be more agreeable in the future when we ask him to go and cool down! The postage was quick also. Thanks very much.