Wingpits?

This comes from a correspondence with my 4th grade teacher; that scenario is a whole topic by itself.

We were driving to school, and Noah was looking out of the window.

Him: "Look, Mom, that bird is going to the playground!"

Me: "It is? What do you think it's going to do when it gets there?"

Him: "Go down the slide!"

Me: "That sounds like fun!"

Pause

Him: "He might get hurt. Maybe he'll go swing on the monkeybars."

Me: "He doesn't have hands, does he? How will he swing?"

Him: "With his feet!"

I'm not quite sure how this transmogrified into the rest of it, but soon the conversation was going like this:

Me: "So the bird is going to hang by his armpits?"

Him: "Yes. No. Birds don't have armpits."

Me: "Why?"

Him: "They have wings!"

Me: "Then what do they have?"

Him: "Wingpits!"

Me: "Excellent! What does Lucy (our dog) have?"

Him: "Nothing."

Me: "Well, she doesn't have arms, but she does have front legs... does she have legpits?"

He loved this concept, and debated strenuously with me about what animals have "legpits" for most of the ride. Tonight when we went to cuddle up in bed, the dog was there, and we investigated her "legpits." And then he tossed his legs in the air over his head and said "Hey, do I have legpits down there?" and I had to tickle him, it was so cute. He seems to agree that the cat has them, but he isnt so sure about the dog.