From Astro Boy to Pluto: The History of “The Greatest Robot on Earth”

It's safe to say that the world of anime and manga would not exist as it does today without the works of Osamu Tezuka—to the point that he has earned the nickname “The God of Manga” in Japan. While he produced numerous classic works during his life that remain popular to this day, one among them has the unique distinction of being the first anime to be aired outside of Japan: Astro Boy.

While Astro Boy was a worldwide hit and contains many well-loved stories, one stands above the others: “The Greatest Robot on Earth.” After being published in the manga, it has been adapted into every anime adaptation of the original story. But even more interestingly, the story so affected Naoki Urasawa (Monster, 20th Century Boys) when he read it at the age of four that nearly 40 years later, he began his retelling of the story with the blessing of the Tezuka family. The result is the critically acclaimed manga Pluto: Urasawa x Tezuka—the subject of Studio M2's Pluto anime adaptation, now streaming on Netflix.

So, with that in mind, let's take a look at the various versions of “The Greatest Robot on Earth” and how the story has changed over the decades.

Astro Boy (1952) – Manga

“The Greatest Robot of Earth” originally ran in Shonen Magazine from June 1964 to January 1965 and is 178 pages in total. It tells the story of Pluto, a robot designed to be the strongest robot in the world. Controlled by the deposed dictator Ababa, Pluto is sent out to fight and destroy those known as the seven strongest robots in the world—which includes Astro Boy himself.

When it comes down to it, this story is about the silliness of the idea that the “greatest” robot (or human, for that matter) would be the best fighter. While Professor Ochanomuzu repeatedly tries to explain this to both Ababa and Atom—that greatness comes in many forms—they both fall into the trap that martial prowess is the key to greatness. Ababa had Pluto built for this very reason, and Atom believes that only by upgrading from a hundred-thousand horsepower robot to a million-horsepower robot will he be able to beat Pluto. However, in the end, Atom's inherent kindness and nobility save the day, not his strength or special abilities.

There's also a prominent theme about humanity's ego and needless hatred. None of the robots have a personal stake in the fight. Pluto is killing the seven strongest robots simply because A) he was ordered to and B) it's what he was designed for. For all the pain and destruction he causes, he is largely innocent in all this. The true evil is the person who controlled him—who used Pluto for nothing but his ego.

Overall, “The Greatest Robot on Earth” is a parable about not letting our base desire for more consume us—about how that is the key to making friends even with those we may see as enemies. It remains a solid and impactful story to this day.

Astro Boy (1963) - Anime

The first anime adaptation of “The Greatest Robot on Earth” is a two-parter, episodes 116 and 117 of the original Astro Boy anime. The first episode is decently faithful and is often frame for frame the same as the manga. However, there are more than a few little changes to keep children entertained. Ababa is now prone to minor pratfalls caused by his hubris, and the episode ends on a straight-up happy ending with Pluto not just sparing Astro Boy's life in their fight but outright saving it.

The second episode is where things go a bit off the rails. Astro Boy's entire character arc from the manga about his need to get stronger is cut. Likewise, so is Epsilon's arc about struggling with the moral implications of killing Pluto through underhanded means instead of in a fair fight.

In this anime, Epsilon and Astro Boy team up to (reluctantly) take Pluto down after failing to talk him and Ababa down. The story's central message is also simplified and made much more kid-friendly. Pluto's death—i.e., his inability to escape his programming to fight—is used to convey the morals that fighting leads only to sorrow, and there is always someone stronger.

Astro Boy (1980) - Anime

Like the 1963 anime, “The Greatest Robot on Earth” is once again spread across two episodes in the 1980 anime—episodes 23 and 24. While the art style has been drastically changed from Osamu Tezuka's original drawings (with at least one important robot getting a complete visual redesign), it is more faithful to the manga overall than the 1963 version of the story—though large portions of the manga's story such as Astro Boy's upgrade and Epsilon's team-up with Pluto remain on the cutting room floor.

This version of the story focuses almost entirely on Astro Boy's internal conflict. Astro Boy keeps thinking he could stop Pluto with one million horsepower. Yet, at the same time, those around him, like Ochanomizu and his parents, keep trying to teach him that raw power is secondary when it comes to what makes people great. Things like wisdom and sense of justice are far more important—and these are qualities that Astro Boy already has.

All this culminates in another new ending. Instead of Astro Boy and Pluto working together to defeat Bora as happens in the previous iterations of the story, Bora easily kills Pluto, and Astro Boy is forced to use his smarts over raw power to defeat the robot that's, on paper, 20 times more powerful than him. To add a second moral to the tale, in the aftermath of the tragedy, Ochanomizu explains that the robots fought and died because people with power always want to show off that power—and will eventually destroy themselves with it. Yet, he believes humanity and robotkind can overcome this flaw and find peace together.

Astro Boy (2003) - Anime

This third animated version of the story is a radical departure from the source material. It takes place over the two episodes “The Rise of Pluto” and “The Fall of Acheron” (17 and 18 in the Japanese airing and 13 and 14 in the American airing). Many characters are recast or cut completely (including Ababa and several of the world's strongest robots). And while several scenes from the original story are reproduced here, much of the overall plot is entirely new.

Rather than a simple tale of humanity's hubris gone tragically wrong, in this version of the story, Pluto is created by Astro Boy's creator, Dr. Tenma, as a foil for Astro Boy. He sends Pluto to defeat the greatest robots in the world to learn from them and evolve himself. Tenma believes that robot superiority over humanity is inevitable and thus wants to create a robot king to rule them. While he hopes Astro Boy will evolve and overcome Pluto, he's also fine with Pluto serving as the future robot king.

This version of the story doubles down on the idea from the original that Pluto isn't evil—the one commanding him is. Because of this, it is much more focused on developing Pluto as a character—with the story as a whole forming a redemption arc for the robot. At first, Pluto is just a fighting machine. However, through his interactions with Astro Boy, Zoran, and the various robots he defeats, he learns about friendship and the need to protect those you care about. Ultimately, he realizes that these are causes worth dying for and sacrifices himself to defeat an evil version of himself that lacks the emotions he has gained throughout his short life.

Pluto: Urasawa x Tezuka (2003) - Manga

Pluto extends the 178 pages of “The Greatest Robot on Earth” into an eight-volume, 63-chapter epic. In it, Naoki Urasawa takes the cartoony world of Osamu Tezuka and grounds it firmly in reality. Rather than being centered around Astro Boy, the story follows Gesicht—a robot detective—as he tries to solve the mystery of why someone or something is killing the seven strongest robots in the world along with their creators.

Instead of a superhero story, Pluto is a gritty crime drama set in a world where robots have rights, but prejudice remains high. In this world, the seven strongest robots were previously tasked with helping the allied nations bring down a dictator building robots of mass destruction. Each murder in the story is used as a vehicle to give us an insight into who each of these robots was—how the horrors of war affected them and how they've attempted to move on in the time since.

What comes out of this is far more than a straightforward murder mystery. Instead, we get an in-depth exploration of the nature of the human soul—especially hatred's place in it. It is a commentary on everything from human rights and racism to the fates of indigenous people and the war in Iraq. Simply put, it is a masterpiece that elevates the themes of the original “The Greatest Robot on Earth” to unimagined levels. It is simply a must-read—and if the animated version is even half as good, it'll be an instant classic.