
(The followings theories are based upon Astro from the 2009 movie, but other adapatations are free to be discussed =3)
Astro is powered by Blue Core Energy, we know that. It’s like a heart, pumping the positive energy around Astro body to keep him alive. The core has even shown signs of being an elixir, (Example: after the Peacekeeper’s destruction, Astro’s arm is damaged, yet after he is revived by Zog this injury vanishes).

Amazing as the Blue Core is, it leaves much up to debate. How much does it contribute to Astro’s functions? Think about it Astro has rocket boots, machine guns. The Blue Core is like an electrical power source, it can’t produce fuel or bullets.
The conclusion? Astro’s rockets must need refuelling, and his machine guns must need reloading, otherwise they'd run out.

Despite being a robot Astro does many human functions, such as eating, drinking and sleeping. Do they benefit him or is he simply wired into feeling that way?
Notice how in the morning Astro sits straight down ready to tuck into his breakfast, but after finding out he’s a robot, he refuses to eat with the kids at Hamegg’s, and instead offers it to the dude next to him. But days later he is seen drinking soda with his friends as they sit on Zog.

Is this an act of just trying to fit in with his human buddies, or did the rumbling in his tummy grow too much to bear?

To able to do this Astro must have a stomach and possibly even taste buds, but it leads on to another question.
Does Astro have a digestive system?
Even more controversial, does Astro go to the bathroom? One would assume this true if Tenma’s intention was to produce a copy of his son to believe he was human.

Astro's speedo and boots are grafted onto him with his flesh. Is it possible this was merely an act of censor (like the way Astro’s clothes are never blown up when he is struck by missiles) or could it be in Tenma’s desperation to have his son back, overlooked this. Either way, if the rocket boots hadn’t given away to Astro he was a robot, then his lacking function to use the toilet and the speedos fused to him would.
Let’s go back to Astro’s energy. The Blue Core is a regenerating power source, but it’s shown a number of times throughout the movie that he can wear himself out. Scenes such as taking on the swarm of robots in the Robot Games, to defeating to Scorpion Brothers, Astro clearly displays signs of exhaustion.
Though he might have something as flashy as the core, it proves Astro like a human being needs to rest, and explains why he sleeps too.

Why he needs to breath is confusing altogether, it’s not like it does him anything useful. Robots don’t need oxygen, yet Astro is seen breathing a whole bunch of (Example: when Astro is deactivated then reactivated by Tenma, or after kicking some robot butt in the Robot Games).

The only thing we can gather is its mere use is to mimic, again for Tenma’s reasons of having a copy of Toby. If Astro didn’t breath he’d of given the game away.
To sum up Astro is too complex for this own good! XD Tenma may as well have paid someone to clone him.
As long as it didn't turn intoStolen Identity 3
