Astro Boy Wiki
Astro Boy Wiki

This article is for the character "Cobalt". For other uses, see Cobalt (disambiguation)

Cobalt is Astro Boy’s prototype and older brother. Cobalt was originally built by Dr. Tenma as a precursor model to Astro, but was rejected due to being "imperfect" and not up to Tenma's standards. Cobalt is later named and activated by Professor Ochanomizu, and Cobalt is added to Astro's family unit as his older brother. He appears exclusively in Osamu Tezuka's original manga and in the 1963 Astro Boy anime series.


Cobalt bears a strong resemblance to his younger brother, Astro. He has black, pointed hair and dresses in very minimal clothing, wearing red knee-high boots, shiny black athletic shorts, and a green belt. However, he is noticeably taller, slimmer and older-looking than Astro, and his hair spikes point straighter upward. His facial features are also different, with a wider, more upturned nose and smaller eyes with less prominent eyelashes.

Personality & Abilities

Osamu Tezuka explaining to Cobalt what happened in the magazine version of "Midoro Swamp"

Cobalt has abilities comparable to that of his brother. Not a perfect copy of Astro, Cobalt runs out of energy quickly when using his powers and being shown to be clumsy. Despite these problems, he is shown to be extremely kind-hearted and loyal. In addition to the abilities that were copied from Astro, in the manga, Cobalt is also shown to have an "Omega Radar" in his chest which emits the same waves as Astro’s radar. With this, he can sense where his brother is and hone in on his location. After the conclusion of the original anime and manga series, Cobalt fell into obscurity, largely due to the fact that Atlas was recast as Astro's "brother" in the 1980s anime, making Cobalt's role somewhat redundant.

Cobalt originally died a heroic death at the conclusion of The Midoro Swamp story arc in the Shonen Magazine serial version of the manga, but Tezuka later changed his mind & rewrote the ending for the paperback version so that he survived.


Cobalt has two separate stories that are very different depending on what version of Astro Boy you are reading or watching.

1963 series

The Anime, in episode 84 (93 in the Japanese version),shows that Cobalt was made before Astro by Doctor Tenma as a prototype, but that he was "imperfect" and was placed into storage. Professor Ochanomizu accidentally overlooked a cleaning schedule at the Ministry of Science and Cobalt was dumped into a scrap heap. Cobalt awakes and right away stumbles into all sorts of mischief. He's shown to be a bit dim-witted when an elderly lady gives him instructions to the Institute of Science and he can't remember them. He's also slow to catch on when people are bad and using him. Unlike the manga, Cobalt isn't shown to have flying capabilities like his brother Astro. On the rare occasion he does, however, he's seen using some sort of strap-on jets.


Cobalt was first introduced the eponymously titled serial, ”Cobalt". In the chapter, after Astro disappears, Professor Ochanomizu made a rough copy of him to defuse a bomb. However, Cobalt's electronic brain isn't as advanced as Astro's and he can't focus on detailed work, like defusing bombs. Professor Ochanomizu notes that "he doesn't have all of Astro's powers" but doesn't explain which of these Cobalt does and does not have. Because he and Astro are made from the same design, Cobalt is sent to track Astro and finds him in the ocean searching for the bomb. Cobalt is shown to have the ability to fly like Astro does.

NOW! Comics series

Astro discovers his prototype

A heavily-altered version of Cobalt appears in issue 1 of NOW! Comics' The Original Astro Boy. In this comic, Dr. Boynton keeps one of Astro's rejected prototypes in the basement of his home. Astro accidentally discovers this robot after hiding from Boynton. The robot is heavily flawed, having clearly melted down at some point, though it still tries to engage in conversation after being reactivated. Astro names this robot "As*@-Clunk" after a noise he makes while trying to speak.

Astro and this robot become friends very briefly. They sneak out of the house and encounter a human girl close to Astro's age, but As*@-Clunk seems to become defensive after the girl calls him "ugly". He takes a doll from this girl and rips its head off, which makes Astro and As*-Clunk fight in front of the girl's house. Eventually, As*@-Clunk experiences a reactor core meltdown within his own power system, and he flies deep into the sky, exploding where he cannot harm anyone else. This marks his last and only appearance in the comic series.