Midoro Swamp is the 34th Episode of the 1963 version of Astro Boy,

I need to clarify that there are actually several episodes of the original 1960s Astro Boy that were considered missing. Of the 193 episodes made, episodes 34, 125, 127, 139, 163, and 191 were lost. Episodes 34, 163, and 191 were eventually found, however, leaving only three episodes (125, 127, and 139) still missing.

Episode 34 is the most infamous of the missing episodes. Originally called “Midoro Marsh” in Japan (it was known as “The Beast from 20,000 Fathoms” in the Fred Ladd dubbing), it aired on Japan’s Fuji Television on August 20, 1963. The episode centers on Astro Boy being sent to investigates sights of dinosaurs in the nearby Midoro swamp after recent events.

Osamu Tezuka wanted to give the staff of Mushi Production a week’s vacation, so they decided to outsource this episode to Studio Zero, an animation studio founded by some of Tezuka’s former proteges, including Shotaro Ishinomori, Shin’ichi Suzuki, Jiro Tsunoda, and the Fujiko Fujio duo. Of all the people listed, Suzuki is the only one with actual animation experience, and thus was the director of the episode. Every other artists were comics people who were juggling their weekly comics deadline while trying to animate.

The results were not pleasant, to say the least. When the footage came back, Tezuka was aghast at what he has seen. He ordered to have the film destroyed, but only until after it aired on Fuji TV. It was also sent to the US as well, for dubbing by Fred Ladd.

The inexperience of the artists involved is very evident. The animation are very poorly done, and Astro Boy’s face seemingly change in every shot in order to suit the cartoonists’ style. Ironically, this makes it easier to decipher who animated what scene.

This wasn’t the last time Mushi subcontracted work to another studio. Episodes 94 through 144 were animated at P Production, a studio that later became known for tokusatsu programs. This was due to Mushi being busy working on shows like Kimba the White Lion and Princess Knight. However, Studio Zero no longer received work from Mushi.

But it wasn’t the end of Studio Zero. They later started employing actual animators on staff and began producing their own shows, mostly in collaboration with Tokyo Movie. The studio existed from 1963 to 1971.

For years, only the US dubbed version was known to survive. An audio track of the Japanese version was later found, which was then inserted over to the picture footage from the US 16mm print.