how does he come up with this stuff?

This story requires a bit of setup. I work at a preschool with a school-age summer program. The building that the school-age class and both 4-year old classes are in is just one big open room - no walls between the three classes. And we share 1 girls' bathroom and 1 boys' bathroom.

Today I took my class to the bathroom, as is our habit before heading off to the playground. Because I don't want to spend the entire recess standing in the doorway so that I can supervise a playground and a bathroom at the same time. Anyway, Z was messing with the keyboard from the school-age music center (which is right next to the bathrooms) and I said "Z, please don't touch that." He came back with a smartmouth mimic and I gave him the "I know you didn't just do that" look. Then Z did the funniest thing.

He stuck his finger out like he was going to scold someone and then turned it to his mouth as he said, "Mouth, don't say that! Ms Amber is my teacher!"