* CreatorBacklash: 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, ''SonicSatam''.
* CrossDressingVoices: 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 [[FamilyMatters Steve Urkel]].
* HeyItsThatVoice: Hey, that's [[FamilyMatters Urkel]] as Sonic! And, oh, I know who's playing Robotnik! It's Creator/GaryChalk, aka [[Anime/UnicronTrilogy Optimus Prime]] and [[AdventuresOfSonicTheHedgehog Grounder]]! Actually, Jaleel White, who plays all three siblings, has said that he uses his Urkel voice for Sonia.
** Also Sonic's singing voice, Creator/SamuelVincent, better known as Double-D in ''WesternAnimation/EdEddNEddy'', Guy Hamdon in ''WesternAnimation/SheZow'' and Athrun Zala in ''[[Anime/MobileSuitGundamSEED Gundam SEED]]'' (among many other roles).
*** Creator/MauriceLaMarche voices Sleet (imitating Creator/PeterLorre) and Athair (imitating Creator/SeanConnery). In particular, Sleet does sound a lot like [[WesternAnimation/{{Futurama}} Kif]].
* NonSingingVoice: All three hedgehogs had three separate Voice Actors for the singing segments - Creator/SamuelVincent for Sonic, Tyley Ross for Manic, and Louise Vallance for Sonia.
* RecycledScript: The episode "Winner Fakes All" has the same plot as the ''WesternAnimation/SonicSatAM'' episode "Sonic Racer", and "Sonic Tonic" is a rehash of the ''AdventuresOfSonicTheHedgehog'' episode "Full-Tilt Tails".
** "Moby Deep" is recycled from the ''TheSuperMarioBrosSuperShow'' episode "20,000 Koopas Under the Sea".
** ''Underground'' wasn't afraid to recycle its own plots either; "the hedgehogs meet a foe pretending to be a friend who ends up being a friend" could describe at least five different episodes.
* TalkingToHimself: Yes, Jaleel White voices ''all three'' main characters.
* WhatCouldHaveBeen: 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 ''ComicBook/ArchieComicsSonicTheHedgehog'', 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 ExecutiveMeddling means that there are some issues are going to have to be dealt with first.
** 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 DevelopmentHell 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 ''SonicSatam''. Instead it was decided to retool the concept completely and make it a separate series, much to his dismay.
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