How does he do it?

Ethan fell asleep in the car today when I was driving home. But what was interesting was that he closed his eyes, and then yawned - which made his pacifier fall out. So with his eyes still closed, he reached down to get the pacifier and he had it about half an inch from his mouth and then he fell asleep and his arm dropped.

How does he fall asleep so fast! And how did he fall asleep while he was in the middle of putting his pacifier back in? Weird baby!