Innocence of children

I was hit by the cute innocence of children earlier today.
I teach English to some kids in Japan, and 2 of them (twins) are taking their class at the same time.
The girl started singing some song at some point which was sounding like "do you like 3, do you like 2"
I have no idea what that song was, but I took the opportunity to teach them about what "do you like" means.
With some examples, do you like pink? do you like apples?
and they made their own example...
That's when the boy said: "Do you like Oppai?"
I had hard time not to laugh pretty hard there, but that’s when the innocence of children hit me, because his sister answered with "Only baby loves Oppai!"
Oppai is where the food comes from for babies, that’s all she was thinking about. That was funny.... not sure if the boy had the same thoughts though lol.