Iz pretends in exactly the same way I used to. He is a rat this morning. He began with simple pretending, crawling on the floor and insisting that he cannot eat with a fork: "Rats eat just with their mouths." (I so need to cut his hair.)
He then asked to watch the animated movie "Ratatouille." Now he is pretending to be in the movie. He does not recite the lines of the movie, but adds his own lines and his own rat character. I used to do this -- though I was more private about it, at least when I reached the age of 8, 9 or 10. And my pretending went on even beyond those years.
Could this be in his nature (as opposed to from his nurturing)? He cannot have learned this behavior from me -- I don't do it anymore. I even tried when I saw "Indiana Jones and the Kingdom of the Crystal Skull" (Indiana Jones movies were a perfect vehicle when I was doing such pretending). Too bad, it was a great way to escape into a different life, a different world.