It’s been a while since I did a strip where the joke grew out of why the characters don’t move. The original idea was that the kid was not getting that the can was empty. But then I figured I could certainly make him dumber than that if I tried.
Having recently heard a few of my “new parent” friends declaring geniuses of their respective bediapered drool-buckets, the rest of the joke followed pretty naturally. But I owe the punchline to the power of internet research, and Wikipedia in particular, as usual. Hail Wikipedia, O embryonic noosphere!
I don’t use the word “O” lightly.