Completely Different Title: Tetsuwan Atom (which means "The Mighty Atom") became Astro Boy in English. This is possibly because there is already a character with that name in the USA.
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.
Fountain of Expies: There's been lots of imitations and variations of Astro Boy around the world over the years, in various media.
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.
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, 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.
And the English version cuts out even more episodes; only 104 out of the original 193 beast 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.
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
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.
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 Ormand 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 Reprisal: 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.