Do you look around at the other adults and think, um, I am clearly not properly adulting here?
I love this way you put it. I had a realization that all of us adults are children whether we realize it or not. We are just playing more serious. But we are all waiting to laugh and play at the moments notice. Some of us are more serious than others so it might take more notice :) Sometimes, when I can think of it, I like to view other adults as children when I interact with them. It makes some interactions more meaningful and entertaining :)
I have had some really powerful teachers around play, and I think play for adults is a big, up and coming field of, um, "research." Our play is different, but when you think of play as something that you become so immersed in that you lose track of time, it becomes more important and more valuable, maybe even crucial to our existence.