I happened to dig into the first comparison tonight, as a test. There's a few things I notice that are constant throughout the English dub:
- The OP/ED have been completely replaced (exchanging about 3:00 for 1:20)
- The next episode preview is removed
- The colours appear faded in most releases
- The screen is cropped to fullscreen. This basically chops a movie-sized screen into a square, cutting off the sides of the scene
- The orchestral soundtrack was replaced with a limited techno soundtrack
- The sound mixing has been converted from stereo sound to mono
- Wally Wingert plays way too many characters. The casting director must have really liked him
The Japanese episodes run for 23:30 to 24 minutes, counting the opening, ending, and preview. Each English episode runs for exactly 20 minutes, counting the opening, ending, and Sony Television's indent. This means that the dub cuts out at least three minutes each time.
The very first edits we get are maybe 2 seconds of Astro's flowing consciousness. Astro calling out, "Father?" has been changed to, "I'm here? Helloooo?" A lot of the travel through his consciousness is silent in the Japanese version, while the dub adds more of Astro calling out.
The scene where Ochanomizu gets out and personally plugs in the lost cable was cut down, losing about 2.5 seconds of a blast of energy knocking him back into the air.
This was a huge edit. The Japanese producers purposely put options for "Atom" and "Astro" on the machine's brand name, which was pretty nifty. In the Japanese version, we get a wide shot of the full logo, and the camera eases in as Ochanomizu decides on Astro/Atom's new name. In the English version, it's a close-up still with the "astro" part centred, with an added blue shine across the word.
With the power plant operator and his lead robot, his dialogue is changed to immediately give away that a massive amount of energy has been lost.
Then, we have the high-ranking scientists coming to visit Ochanomizu and Astro. It may not have been intentional, but the fullscreen cropping seems to hide a female scientist.
This scene of Astro playing with blocks is removed. Clearly this triangle-on-square violence was deemed inappropriate for the children of the early 2000s.
This whole scene loses about a minute. Astro honks Ochanomizu's nose, and the scientists can't seem to understand why Astro is supposed to be so advanced. The scientists are unprofessionally catty in the dub.
Astro talks throughout this scene in the dub, which is strange, because he originally silent. He's full of X-Treme Attitude, like a little Sonic the Hedgehog. Sometimes this makes the series funny, sometimes it makes him too mean and not the innocent hero kid we know.
Yuko comes in to call Ochanomizu back to work, referencing a late meeting in the dub. A cut shot (above) has Yuko exclaiming that Ochanomizu should leave Robita/Nora to watch Astro, and Momo squawks. Yuko sounds way younger in the Japanese audio, like she's maybe 20-24 years old.
The music while Astro explores is really peppy and cute, and fits better than in the English dub.
Astro's 'tude gets a little over the top when he climbs up the ventilation shaft. He doesn't say anything in the Japanese track, but in the English, he says, "I'm supposed to be learning, right?"
Robita/Nora originally yells at him to get down, but is dubbed into, "My circuits can't take it!"
Astro responds with, "Don't blow a gasket!" right before Nora smashes her head on the vent opening. Rude.
The dub adds an "establishing shot" of power plant, which is just a reversed clip of the pan down to Magnamite. There's a repeat of the clip where the station operator talking to a robot, which then cuts into the shot of him yelling on the vidcom screen. In the dub, Power Guy tells Ochanomizu/O'Shay that the police called him and he told them it was O'Shay. However, in the subtitles, he's only scolding Ochanomizu for being irresponsible and threatens to file a report. This added footage adds about 5 seconds.
Another line change is when Tawashi demands an explanation for the power outage. Instead of Ochanomizu stuttering, he answers, "I can't sleep with the lights on?" This joke does work for how goofy he can be, but it undermines what a dignified genius he is.