I agree with this; Atom's naiveté is appealing, especailly since I have no children of my own. However, I must say that it is very unrealistic in that the child's naivé ideals win in the end, rather than being shown as the simplistic and unrealistic presumptions of one who has yet to learn the ways of the world.
Thus, nobody should regard Astroboy stories as anything but fantasy in this regard. However, Tezuka did use them as [url=
http://www.thefreedictionary.com/allegory]allegories[/url] for subjects too controversial to otherwise cover. Discrimination against robots being an allogory for racial discrimination, etc.
As children go, I think the 2003 version made Atom & Uran more childlike; in the 50 episodes they did things that kids do as much as they did in 193 episodes in the B&W series. Although Atom is depicted mainly as stifling Uran's fun, telling her to 'behave,' etc., he does play sports with other boys. However, the only imaginative play that I recall was in the B&W series.
In 70 Raffalsia (61 Flower Monster) Uran pretends to shoot Atom, who then performs one of those extended death scenes so frequent in old Western films. He does the same thing in
Lonely Atom, when he meets a little boy whose only friends are animals. I cannot recall any other incident of pretending, in any series, though.
