It specifically goes over three separate games:
- Sister Sonic, which was not meant to be a Mean Bean Machine-esque reskin of Popful Mail solely for overseas audiences but an outright remake for the Sega CD that would've released worldwide as a Sonic game (which turned into a more faithful remake after Popful Mail fans "vehemently protest[ed]")
- A sequel to Sonic Chronicles, an RPG on the DS by BioWare that ended on a cliffhanger and inadvertently provoked a lawsuit from Archie Sonic writer Ken Penders that killed any further continuation
- Sonic Day, a mobile game by Nitrome based on their hit platformer Jump Day -- Sega of Japan ultimately passed on it
(I actually wrote up a full summary of the video, but Lemmy wouldn't let me post it here.)