Wheels
A friend of ours was visiting with Jonah and asked: Brian: What has wheels? Jonah: My bicycle Brian: What else has wheels? Jonah: Another Bicycle. We had a good laugh but Brian, being a teacher by nature and profession, wasn't quite done with the lesson. He found a dirty yellow Tonka dump truck and brought it over. Brian: What things have wheels? Pause. Pointing at the dump truck. Brian: What about this? Jonah: No. This truck has 4 tires.