The scary thing is that he says it with *exactly* the same inflection that I say, "Not yet!" when he wants to do something Right Now that he can't at the moment, but can later.
Cool thing, and possibly too much information for non-parent types was that when John and Jet were outside, Jet was farting a lot, and John asked him if he was poopy and Jet said, "Poopy yet!" and, sure enough, he hadn't actually dirtied anything, yet. Ten minutes later, and he'd done the deed, so it looks like potty training is probably the next item on the list of Things to Learn and be independent of, since Jet can communicate the feeling, now. I'll be glad to be free of diapers.