Jetter Mars was an interesting self-ripoff case where Tezuka recycled Astroboy's concept in a hurry to create a new TV series. Despite the obvious similitudes, Jetter Mars had some interesting details, Like Jetter's ability to grow like a normal kid and ever having dreams while sleeping. He also appeared in the GBA game and his conversation with Astro Boy only can be described as a funny, epic lampshade.
Late Export for You: Astro Boy manga wouldn't be translated in English and released in the America until 2002 when Dark Horse Comics have acquired the rights, but just years after the death of the creator, Osamu Tezuka. They also noted before they published the manga in that year, there's two unlicensed American comic adaptions that's not drawn by Tezuka, existed.
"An American-style Astro Boy comic book was produced under the Gold Key imprint in 1965, but it was not drawn by Tezuka, and it was based on the animated TV show. In the 1980s, another unlicensed English-language Astro Boy comic book was created, but it too was not drawn by Tezuka. As a result, until the publication of the series by Dark Horse Comics in 2002, English-speaking fans of Astro Boy have had no way of knowing what the original manga story - the original Mighty Atom - was like."
Missing Episode: Two story arcs from Mighty Atom Club magazine, "Jungle Devil Boundary" and "Chi-Tan", have never been reprinted (in Japan or otherwise).
What Could Have Been: When Tezuka was able to meet Walt Disney in person at the 1964 New York World's Fair. Walt discussed about doing a collaboration movie with Tezuka and told him "If you have time, visit me in Burbank." after he revealed that he's seen the 1960s incarnation of Astro Boy in Los Angeles. The idea was never revisited again, and quickly died after Walt's passing in 1966.
Science Marches On: "Ivan the Fool" depicted the Moon having frozen air on it which was let free by the sun rising, allowing humans who were stranded there to live until the sun set. We now know this not to be the case.
1963 TV series
Creator Backlash: According to a commentary on one of the 60's Astro Boy DVD boxsets, Osamu Tezuka hated one particular episode, "Midoro Swamp" aka "The Beast from 20 Fathoms". He farmed out the episode to a group of young anime/manga students (specifically to Studio Zero, whose employees included Shotaro Ishinomori and the Fujiko Fujio duo), and the results dissatisfied him so much, that he personally destroyed every possible copy he could find. Unfortunately for him, a copy of that episode had already been shipped to the U.S. and dubbed (and would later resurface as a "Lost Episode" of the series on VHS), and the Japanese soundtrack (but not the footage) still exists and was included as an extra in the episodes release on the Astro Boy DVD sets.
The Midoro Swamp episode is usually cut from re-releases because it was poorly animated, even by the standards of the time.
And the English version cuts out even more episodes; only 104 out of the original 193 were ever dubbed. This is because the American dubbers had become increasingly worried about the violence in the show, America and Japan having taken Astro Boy in rather different directions, and a combination of fatigue over this and cultural differences in approach to animated stories (Japan wanted to resolve the story, America decided that 104 episodes was plenty to allow for reruns) resulted in the American studio cancelling its contract. Osamu Tezuka himself had grown tired of working on Astro Boy and wanted to pursue other stories, hence why even the Japanese version ended at episode 193.
No Export for You: Only 5 episodes of the Japanese-language version have been released in North America as bonus features on the Nozomi Entertainment dub DVD releases, meaning that all but one of the episodes that weren't dubbed haven't been released at all in that region.
Kazue Tagami voiced Astro in episodes 97-106 while Mari Shimizu was on maternity leave.
Uran was first voiced by Yoko Mizugaki, then by Reiko Mutou, then by Kazuko Yoshikawa.
Higeoyaji was first voiced by Masaaki Yajima, then by Ayao Wada.
Tawashi was first voiced by Shingo Kanemoto, then by Kouichi Chiba.
Self-Adaptation: Osamu Tezuka opened his own animation studio to produce this show, even writing and directing several episodes.
Adult Swim aired the show as late-night filler, though only 52 episodes were aired. Curiously, it was showcased on the April Fools Day 2012 Toonami broadcast along with Trigun, despite both shows not having aired on Toonami before.
1980 TV series
Channel Hop: The original series (and the 2003 series) aired on Fuji TV, the 1980 series on the other hand aired on Nippon TV.
Keep Circulating the Tapes: There exists an English-language dub, produced exclusively for Canadian broadcast, colloquially referred to among fans as the "Canadian" version of the show. Unlike the more widely-known American dub, which has been used for the DVD releases, the Canadian dub was only ever broadcast within Canada up until the early 1990s and hasn't seen the light of day since. A few episodes have surfaced online, but it seems highly unlikely that an official release will ever materialize, as the American dub is already available, and the whereabouts of the Canadian version, if the master tapes even still exist, is unknown. The Canadian dub featured a different voice cast than the American one, gave many characters different names and contained additional editing (episode runtimes were shorter). It also featured a trivia game at the end of each episode, wherein Astro gave a recap of the plot, but would intentionally include an error for viewers to find. The answers were never revealed on the show; ideally viewers were instructed to write down what they believed to be the error and compare their answer with those of their friends.
The American English dub, while staying mostly faithful to the Japanese version, has notoriously cut and edited the first two episodes of the Japanese version into one episode in the dub, effectively cutting out Atlas's origin story (meaning in the dub he wasn't introduced until later in the series and his past was only shown through flashbacks). The dub has been released on 2 separate DVD sets in different regions, a release in Australia by Madman, which along with all the dub episodes, including the first two uncut Japanese episodes with English subs. The other set released in the US by Manga Entertainment, while it had all the episodes in subbed and dubbed forms, the Japanese version of the first two episodes was cut like the dub version. Thus far, it is hard, if not impossible, for US fans to see the first two uncut episodes of the series. Unfortunately, both English DVD sets are out of print as of 2012.
Sort of. On the dub's DVD release, the episodes are for the most part wildly out of order. And there isn't a Japanese language track or subtitles. The dub is pretty good all things considered, but it's hard to ignore this stuff.
Furthermore, in a crossover with Macekre while the episode count is the same as the Japanese version, one of them was replaced by a Clip Show episode.
Also, while the show was produced in widescreen, the dub was cropped to 4:3 for all its releases.
Dueling Dubs: This anime adaption have a few of Chinese dubs. One is for Taiwanese Chinese version (which also translated the title opening song, see here.), one is for China Golden Eagle Cartoon channel version (which the only Chinese dub to cover the entire series), one is for CCTV-14 version, and, one is for Donghexing VCD dub (which based off the edited English dub, you can see here)
Missing Episode: Dub only - the 20th episode "Eternal Boy" has been omitted from release with the rest of the series in Digital and DVD form, mainly because the plot revolves around the Peter Pan story, which is still under copyright by Great Ormond Street Hospital in the US and UK. It was replaced with a clip show episode, with Tenma and Shadow discussing Astro's progress up to that point in the series.
Role Reprise: Hisashi Katsuta, who voiced Ochanomizu in the previous two anime adaptations, voices him once again in this series.
Three Laws-Compliant: While the movie makes much ado about robots like Astro being compliant to The Three Laws, Osamu Tezuka had his own set of robotic laws in Astro Boy not based upon Asimov's Three Laws. Under Tezuka's Ten Principles, Robots could not change their assigned gender, create money, assemble robots disassembled by humans, leave the country without a permit, or other such things.