Ever since “;Tetsuwan Atomu”; (”;Mighty Atom”;)—better known as “;Astro Boy”; in the U.S.—first appeared in the pages of Shonen magazine in Japan in the 1950s, generations of Japanese and American fans have been entertained by the little robot's adventures.

Manga artist Osamu Tezuka died in 1989, but the legacy of one of his greatest creations endures to this day. The theatrical release of Imagi's computer- animated “;Astro Boy”; movie this weekend is proof of that.

Whether this film will be embraced by audiences (see: everything made by Pixar to date) or dismissed as just another soulless computer-animated feature (anyone remember “;Space Chimps”; or “;Battle for Terra”;?) won't be known until the weekend box office receipts are tallied up. There's little doubt, though, as to what's considered one of the best “;Astro Boy”; stories ever told: the appropriately named “;Greatest Robot on Earth.”; It's a story so nice, it's been told twice—once by Tezuka between June 1964 and January 1965 in Shonen magazine, and once by Naoki Urasawa in “;Pluto,”; serialized between September 2004 and April 2009 in Big Comic Original.

But the approaches these two highly regarded manga masters took with the source material are very different.

Tezuka's version—available in the U.S. in volume 3 of Dark Horse's “;Astro Boy”; translation—is the more action-packed of the two. In Tezuka's story, a sultan builds the robot Pluto and sends it on a mission to battle and destroy the world's seven strongest robots, thus claiming the title of “;world's greatest robot”; through brute force. Astro, naturally, is one of the targeted robots.

Pluto tears through the other robots in short order, but Astro proves to be different. Part of that difference lies with Professor Ochanomizu, Astro's human mentor, who insists that the two robots not fight when they first meet—an order that Pluto reluctantly agrees to follow. Astro believes the rest of the difference is in their power levels, begging for a boost in horsepower from 100,000 to 1 million so he can fight brute force with brute force. But the true comparison is in the level of compassion Astro has, first in caring about his sister and the professor when they're both kidnapped, then in his concern for Pluto when he's damaged in a fight.

It's in this difference that Tezuka plants his fundamental question of why humans create powerful technology simply to destroy or be destroyed in the race to achieve superiority. Even the sultan is left to question at the end the point of such a pursuit of power, and Astro hopes for a day when he won't have to fight other robots and they can all be friends.

In Urasawa's “;Pluto”;—currently being released in the U.S. by Viz—the primary focus shifts from Astro to another of the seven powerful robots, the German police robot Gesicht, and his investigation of a series of murders of robots and humans alike. By contrast, Astro—called “;Atom”; in this translation—is a robot that looks like an average human boy, albeit one with exceptional reasoning and peacekeeping skills.

This fundamental shift transforms the story from an action-adventure designed mostly for a young audience into a more mature murder mystery. The art style differs accordingly—while Tezuka uses a cartoony style influenced by Disney and other popular U.S. comics and cartoons of the era, Urasawa employs a more realistic style. Seeing some of Tezuka's characters rendered with the added bulk they would have if they existed in real life is truly a marvel.

The basic concept of Pluto destroying the world's greatest robots remains the same—Urasawa designed his series as a tribute to Tezuka and his original story, after all, even going so far as to announce he was starting work on the series in 2003, the year of Astro Boy's “;birth”; in Tezuka's canon.

But the slower pace of “;Pluto”; affords Urasawa the chance to really play with his cast of characters and develop them further. It also gives him a chance to use the style of fractured storytelling that worked so well in the two series he worked on prior to “;Pluto,”; “;Monster”; and “;20th Century Boys,”; in which the narrative will follow a series of events for a while, cut away to something seemingly completely unrelated and then slowly tie itself back into the big picture.

This form of storytelling adds a layer of suspense to the proceedings—while Pluto is revealed within the first few panels of Tezuka's story, we only get fleeting glimpses of him in Urasawa's story, turning him into more of a sinister presence.

Urasawa adds more emotional depth to the proceedings. The death of the first robot, Mont Blanc of Switzerland, is dealt with in six panels in Tezuka's version; in “;Pluto,”; Mont Blanc's death resonates as an international tragedy that is only compounded throughout the series with the subsequent deaths of other robots.

These robots have friends, families, admirers ... as well as detractors, in a commentary on race relations and the meaning of what it means to be human and the rights afforded to such an existence.