History YMMV / SonicUnderground

* CrossoverShip: There's a small subset of fans that ship Sonia with Shadow the Hedgehog or Espio the Chameleon from the [[Franchise/SonicTheHedgehog main continuity]]. Alongside that, Manic with Scourge the Hedgehog from [[ComicBook/SonicTheHedgehogArchieComics Archie Sonic]] has its fans too.

** During the episode song of "Winner Fakes All", Sonic briefly runs past and nearly accidentally flips up the skirt of a human girl, one of the few of a human other than Robotnik, and the only one that isn't just background filler, which is given no explanation whatsoever.

** In "No Hedgehog is an Island", when Dingo double-crosses Sleet and plans to become ruler of Mobius himself, Sleet objects on the basis that "[He] can't even drink a glass of water without using both hands!". 21 years later, UsefulNotes/DonaldTrump drinking a glass of water with two hands was seized upon by opponents for jokes and as a sign of him being physically unfit for office.

** By the time the series premiered, fans were used to Creator/JaleelWhite's voice as Sonic. The voice he used for Manic isn't too bad, either, and sounds distinct from his brother's. But having White voice ''Sonia'' is really pushing it and a prime source of {{Narm}}. She sounds an awful lot like Sonic pretending to do a woman's voice and failing. Most agree that her singing voice, Creator/StevieVallance, sounds ''much better'' in the role and should have voiced her full time.
** Knuckles' voice sounds like a nasal, slightly higher version of Manic's voice, even though a deeper tone would better suit the character. And this from Creator/BrianDrummond, known for [[Anime/DragonBallZ Ocean's Vegeta]] of all characters!

** "Bug!" is about a swarm of robotic flies with the ability to brainwash people with a serum, including Manic. This could've been a great opportunity to have the bonds of characters grow stronger as they try to deal with Manic's brainwashing, but they quickly find out and Robotnik gives up as soon as he loses connection with Manic.
* ThisIsYourPremiseOnDrugs: The show follows the Sonic versus Robotnik formula… featuring Sonic's long lost siblings and fighting him with ThePowerOfRock. Beyond a few elements from the games, the show is really InNameOnly when it comes to its connection with Sonic.

** Manic is a thief who is also a high-tech specialist who rides a HoverBoard, all of which anticipates the Babylon Rogues of the ''VideoGame/SonicRiders'' series.

** While Sleet is shown to be a reasonably competent villain, his Creator/PeterLorre-esque voice makes it hard to take him seriously a lot of the time.

** The exploding baby hedgehog robot. ''All of it.''

* TheyWastedAPerfectlyGoodCharacter: The role of GadgeteerGenius Cyrus could have easily been filled by Tails.

** "Winner Fakes All" has Robotnik trying to build a robot that can outrun Sonic in order to lead the heroes into a trap. This would've been the perfect way to introduce [[KnightOfCerebus Metal]] [[{{Archenemy}} Sonic]], but no, instead it's just a generic, turtle-looking robot that serves no purpose to the overall plot and is defeated comfortably.

* AudienceAlienatingPremise: There are many ''Sonic'' fans who couldn't get into it even back when it was new, let alone in the modern age; on one hand, some fans were still bitter that there wasn't a season 3 of ''[[WesternAnimation/SonicTheHedgehogSatAM SatAM]]'', and this was on top of it being different from the games even at the time. On the ''other'' hand, the show came out shortly before ''VideoGame/SonicAdventure'', itself different from ''Underground'', changed the direction of the franchise for years to come. Basically, the show is an oddity no matter how you look at it, since it doesn't exactly gel well with what came before ''or'' after it.

** The Oracle of Delphius could actually be [[TheManBehindTheMan the true Big Bad]] of the show. He has amazing powers and [[WhyDontYaJustShootHim could have killed Robotnik in his own bedroom]] as shown in a flashback in the first episode, but he instead gives him the heads up about the prophecy, which gets Robotnik to start looking for the trio. Also in the same episode, if he hadn't directed the trio to meet at a public place then their foster parents would have been safe and not turned into robots; as if the Oracle is going with an "I'll finish off whoever is left in the end" approach. Alternatively, the Oracle just [[{{Troll}} likes to mess around with people]]. Alternatively, he doesn't do any of those things because averting from the prophecy would make it not come true.

* QuestionableCasting:
** By the time the series premiered, fans were used to Creator/JaleelWhite's voice as Sonic. The voice he used for Manic isn't too bad, either, and sounds distinct from his brother's. But having White voice ''Sonia'' is really pushing it and a prime source of {{Narm}}. She sounds an awful lot like Sonic pretending to do a woman's voice and failing. Most agree that her singing voice, Creator/StevieVallance, sounds ''much better'' in the role and should have voiced her full time.
** Knuckles' voice sounds like a nasal, slightly higher version of Manic's voice, even though a deeper tone would better suit the character. And this from Creator/BrianDrummond, known for [[Anime/DragonBallZ Ocean's Vegeta]] of all characters!
** While Creator/MauriceLaMarche was a good casting choice for Sleet, the decision to have him sound like Creator/PeterLorre doesn't match Sleet’s character at all. Tellingly, many dubs, such as the German dub, give Sleet a deeper and more respectable voice.

* UnpopularPopularCharacter: Sleet and Dingo are surprisingly popular. Blame it on their fun voice acting and their [[Anime/PokemonTheSeries Jessie and James]]-like appeal.

* WTHCastingAgency:

** The Oracle of Delphius could actually be [[TheManBehindTheMan the true Big Bad]] of the show. He has amazing powers and [[WhyDontYaJustShootHim could have killed Robotnik in his own bedroom]] as shown in a flashback in the first episode, but he instead gives him the heads up about the prophecy, which gets Robotnik to start looking for the trio. Also in the same episode, if he hadn't directed the trio to meet at a public place then their foster parents would have been safe and not turned into robots; as if the Oracle is going with an 'I'll finish off whoever is left in the end' approach. Alternatively, the Oracle just [[{{Troll}} likes to mess around with people]]. Alternatively, he doesn't do any of those things because averting from the prophecy would make it not come true.

** During the episode song of "Winner Fakes All", Sonic briefly runs past & nearly accidentally flips up the skirt of a human girl, one of the few of a human other than Robotnik, and the only one that isn't just background filler, which is given no explanation whatsoever.

%%** '''[[WebVideo/{{Tamers12345}} Bartleby]].'''
** Sonia, Manic, and to a lesser extent Aleena are this for the entire franchise, as many fans like them and use them in fan works, even if they are not familiar with or even fans of Sonic Underground as a whole.

** One episode has Sonic playing tennis against himself, and throwing a [=McEnroe=]-esque tantrum when the umpire (also himself) makes a call against him. Twenty years later, the [[https://www.youtube.com/watch?v=szby7ZHLnkA second trailer]] for the [[Film/SonicTheHedgehog2020 film adaptation]] has Sonic playing both table tennis and baseball against himself.

** Jaleel White voices Sonic, Manic ''and'' Sonia. As one might expect, he does fine with the first two, but Sonia ends up sounding like a cross-dressing [[Series/FamilyMatters Steve Urkel]], which neuters any scene she has that's meant to be taken seriously.

** By the time the series aired, fans were used to Creator/JaleelWhite's voice as Sonic. The voice he used for Manic isn't too bad, either, and sounds distinct from his brother's. But having White voice ''Sonia'' is really pushing it and a prime source of {{Narm}}. She sounds an awful lot like Sonic pretending to do a woman's voice and failing. Most agree that her singing voice, Creator/StevieVallance, sounds ''much better'' in the role and should have voiced her full time.

** Likewise, while Sleet is shown to be a reasonably competent villain, his Creator/PeterLorre-esque voice makes it hard to take him seriously a lot of the time.

** The many, ''many'' wonky [[SpecialEffectsFailure animation errors]].

** By the time the series aired, fans were used to Creator/JaleelWhite's voice as Sonic. The voice he used for Manic isn't too bad, either, and sounds distinct from his blue brother's. But having White voice ''Sonia'' is really pushing it and a prime source of {{Narm}}. She sounds an awful lot like Sonic pretending to do a woman's voice and failing. Most agree that her singing voice, Creator/StevieVallance, sounds ''much better'' in the role and should have voiced her full time.

** Similar to Knuckles' casting, Creator/MauriceLamarche was a good casting choice for Sleet on paper, only to then make Sleet sound like Creator/PeterLorre, despite that kind of sniveling voice not matching Sleet’s character at all. Tellingly, many dubs such as the German one give Sleet a deeper and more respectable voice.

** '''[[WebVideo/{{Tamers12345}} Bartleby]].'''
** Sonia and Manic could be considered this for the entire franchise, as many fans do like them and use them in fan works, even if they are not familiar with or even fans of Sonic Underground as a whole.

** By the time the series aired, fans were used to Creator/JaleelWhite's voice as Sonic. The voice he used for Manic isn't too bad, either. But having him voice ''Sonia'' as well might not have been the best decision. She sounds an awful lot like Sonic pretending to do a woman's voice and failing.

** Similar to Knuckles casting, Creator/MauriceLamarche was a good casting choice for Sleet on paper, only to then make Sleet sound like Creator/PeterLorre, despite that kind of sniveling voice not matching Sleet’s character at all. Tellingly, many dubs such as the German one give Sleet a deeper and more respectable voice.