When my son was about 2 or 3, he wouldn’t go to sleep, so I let him in my bed.
My husband was asleep so I told my boy he had to look at his books quietly while I read mine. He was good for a bit but then he started reading the book.
Actually reading the words out loud. Slowly.
He couldn’t read and it was a newer book we hadn’t read to him yet. It wasn’t memorization.
I asked him how he knew what it said and he replied “my friend John is telling me”. Scared the shit out of me.