I am totally serious about this. I was going through the Sakuga Wiki's list of technically impressive animation, and there it was again. The animation in Sonic CD absolutely blew my mind as a kid: it made me feel like I was right in getting a Sega CD for my birthday (I was right about Sonic CD, of course, just not about the console) and it was one a thousand tiny childhood brushes with anime/manga that planted the seeds of what would become an obsession.
Though this video leaves out a few cuts, it contains most of the animation that Toei and Studio Junio did for the game: an opening, an ending, and the scenes that played over the ending credits. I used the Japanese version music not out of any hate for the US version opening theme, Sonic Boom (quite the contrary!) but out of love for the JP version ending theme, Cosmic Eternity.
Something to keep in mind about this animation is that it absolutely did not need to look as good as it did. I don't mean that because a videogame was somehow unworthy of such high-quality work: I say that because of the Sega CD itself. As one of the first mass-market consoles capable of displaying full-motion video, video playback was very early and very rough.
This is how that animation actually looked in the game. The Sega CD didn't even have powerful enough hardware to display video that filled the screen, so video had to be displayed in small letterboxes and the animation you see on the screen is way scaled down from the original work. In particular, the credits scenes are tiny! I get the feeling that the scenes were animated anticipating this loss-- there isn't a lot of shading on the characters, for example-- and that scaling down the animation for the SCD was likely quite an undertaking itself.
The reason we have high-quality video of these scenes is that Sonic CD was later ported to consoles that could better handle video, and they're a revelation, aren't they? There are all kinds of little details (particularly in the opening) that never would have made it to my eyes from the muddy Sega CD video. One has to wonder why they did all the hard work in the first place, or hell, how they were able to.
Compare this blowout to recent anime studio collaborations on videogames: Studio 4C's totally shameful work on Street Fighter IV, or Gonzo's good but very brief scenes for the Blazblue games. I suppose it was a different time for the Japanese animation industry.
Nothing can survive the way you stay alive!