Creator Backlash: Ben Hurst expressed a contempt for writing for the series, disliking the premise and having a bad time working with the material of other staff. To add insult to injury, this was pitched in favor of continuing his previous beloved project, Sonic SatAM.
Cross-Dressing Voices: Jaleel White as Sonia. Oddly though, if one watches an episode of Sonic Underground, you can tell the voice Jaleel White uses when providing the voice of Sonia sounds inconspicuously identical to the high-pitched voice White used from his other (more) famous role as Steve Urkel.
Non-Singing Voice: All three hedgehogs had three separate Voice Actors for the singing segments - Samuel Vincent for Sonic, Tyley Ross for Manic, and Louise Vallance for Sonia.
What Could Have Been: More episodes of this show were planned, but never went beyond the planning stages. We can only wonder how it could have ended. Ian Flynn, current head writer of Archie Comics' Sonic the Hedgehog, has stated that he would like to write a conclusion in comic form (helped by the fact that the cartoon was established to be in the comic series' Multiverse in an earlier story), but Executive Meddling means that there are some issues are going to have to be dealt with first.
Early concept art shows Queen Aleena (a.k.a Sonic's Mom) with a different design.
At first, it seemed he would finally get to make that ending. It was even briefly advertised to be in the fiftieth issue of Sonic Universe. However, a different story ended up taking that slot, and the conclusion went through Development Hell before it was eventually cancelled. A summary of the story will appear in "Lost Hedgehog Tales," a collection of Ian's planned and scrapped stories.
According to Ben Hurst, this series would have at one point been a continuation of Sonic SatAM. Instead, it was decided to retool the concept completely and make it into a separate series, much to his dismay.