Once there was a puppy and a kitten who lived together in their owners' house. They would often go out into the garden to look for snails. When they found some, the puppy and kitten would play with them as though they were balls. One day, they decided to put on a big tennis tournament, so they called all their friends around, and formed teams. However, just when they were about to start, the snails refused to be treated like tennis balls. So everyone went running, looking for some tennis balls for their tournament. One animal brought a stone, but they could see that it didn't roll. Another brought an orange; the orange rolled but it didn't bounce. Someone else brought a frog. There was no doubt that the frog bounced, but unfortunately it didn't roll. Another animal came with a football, but that was too big. Then someone found a smaller ball, but it was black, and no one could see it very well. Finally, they found a small tennis ball. It was round, bouncy, green, and easy to see; and so began the tournament. I can't tell you who won, because after so much time spent searching, the animals had tired themselves out, and everyone who started playing was soon lying asleep on the court! 
Teaching very young children about different sizes and shapes. 