I read about this in a Russian puzzle book and I don't think it's been posted before.
A soccer goalie had just lost an important match, and when he went to sleep that night he had a strange dream. He dreamt that he was kicking a soccer ball against a wall, and as he did so, the soccer ball got bigger and bigger, and the goalie got smaller and smaller. Suddenly, the goalie turned into a ping-pong (table tennis) ball and the soccer ball turned into a massive hard exercise ball. The exercise ball rolled around, trying to crush the ping-pong ball. Without leaving the floor, is there any way the ping-pong ball can prevent being crushed?