I propose that Atom and Uran could eat, taste and "enjoy" food, and the food they consume could be converted by cold fusion into energy (Think of the "Mr. Fusion" machine fitted onto the DeLorean in "Back to the Future" - they could put ANYTHING in there and it would be converted into energy for the car).
I say it's time for A & U to REALLY step into the future. Eating food would ABSOLUTELY make them more human.
So would real hair. Even as a child, back in the 60's I felt it was a serious flaw in the anime that Atom had shiny skin and hair (same for Uran). I propose the "updated" Atom and Uran would have the ability to have "skin" that "shifts" from robotic, painted-on costumes and hair, to natural skin and human hair (with all the things Atom flies through, he's bound to burn off actual "hair"

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Finally, I am TOTALLY for growing them up - especially Atom. I always felt THAT was why Tenma freaked out to the point of disowning his robot son. Now, HOW that would be accomplished, I can't say - but I always supposed that Atom would grow a bit, and his voice would change, and then Tenma would relocate his AI into a "teen" body, and later an adult body.
Beyond the fact that there are a LOT of stories (including romance for the fangirls) that be appropriate with Atom as an adult, just think about how illogical it is for a person with Atom's intelligence to want to stay 9 years old. How long do you remain in 4th grade?

What happens when your best friends grow up? Why would you remain in school - do you stay in the same grade (in the meantime, Atom is a genius, so he'd be intellectually moving forward).
Just because he's as cute as can be as a little boy doesn't mean he can't grow into a mature character with as much to offer. Think of how they did the reverse with Superman . . . after the adult character was established, they created a whole "prequel" series called Superboy.
I know Tezuka "addressed" this matter, but this is one place I respectfully disagree, and feel a whole other universe of adventures were left untold by simply not letting Atom grow up (and the name Atom works better than "Astro Boy" in that situation, for sure!

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