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.
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.
[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
Hey, It's That Voice!: Mari Shimizu reprised her role as Astro. Hisashi Katsuta also reprised his role of Ochanomizu.