Motherhood and the regression of my intelligence

I and Cru's ongoing argument:

ME: "Cru do not unlatch your seatbelt." (it doesn't really matter what I say his response is still the same)

CRU: "Mom you just said poopies!"

ME: I did not say poopies or anything reminiscent of it I made reference to your seatbelt!

CRU: " You said poopies!"

ME: Cru! I did not!

CRU: Yes you did!

ME: "NO I DIDN'T! Nor have I ever said poopies! Stop saying that!

CRU: (laughing) You said poopies!

ME: I DID NOT SAY POOPIES!!!!!"

And so the intellectual battle continues.....

And in other news....so does the confusion...

Sage will not walk and its frustrating me. The confusion is that she won't walk,

but she will do this:

Open the toilet lid, climb up and sit in it.

I don't understand.