* AlternativeCharacterInterpretation:
** Was Chaos initially willing to go along with Eggman's plan? Or was he just an opportunist using the not-so-good Doctor until he no longer needed him? Did he finally turn on the doctor for [[YouHaveFailedMe letting him down too often]] or for [[DirtyCoward leaving him to his fate on the downing Egg Carrier]]?
** Is E-102 Gamma's consciousness unique to his programming as an Eggman robot, or does it originate from the bird inside him? There is evidence that points to the former, but Gamma's ability to remember the bird's family at the end of his story lends credence to the latter interpretation. Regardless of the answer to this question, it has important implications toward Gamma's decision to "rescue" his E-series brothers by destroying them, as it paints Gamma's mission in one of two ways: either he is on a genuinely fratricidal crusade to "liberate" his friends from being used for Eggman's machinations by outright killing them, or he's unambiguously saving them by freeing their true selves. The latter is supported by the loading screen recaps, where he explicitly says he will destroy Eggman's "evil machines" and rescue the animals. This also changes the ending: is Gamma's flicky accompanying Amy fulfilling the promise they would meet again and showing that Gamma live on in a way, or is it just the bird thanking her for taking care of its child? The correct answer might be [[TakeAThirdOption some of both]].
** [[spoiler:E-101 Beta's LastBreathBullet: Was this an instance of EvilIsPetty where Beta refused to be the only loser in his second battle with his brother, or was he on the same self-appointed mission as Gamma to liberate his brothers and killed him for the same reasons Gamma killed him?]]
** The lyrics to "My Sweet Passion" are so nonsensical that it has various interpretations. Some view them as being about Amy being a {{fangirl}}ish DirtyKid while others think they're about how Amy's desperate for Sonic's attention and would change herself for his sake.
* AluminiumChristmasTrees: The shower stalls in Casinopolis--an actual fixture at casinos, at least in the US.
* AnnoyingVideoGameHelper:
** Tails tags along in Sonic's levels, usually picking up things you don't want, like animals that you can take into the Chao Gardens if you're only looking for specific ones to give to your Chao so that they take only the traits of those specific animals, among some other undesirable moments.
** Tikal. Hitting her not only gives you useless hints, it also stops your movement, leading to time loss or even death if you are in mid-jump in front of a {{Bottomless Pit|s}}. There are levels that have to be solved without using hints, so running into her forces you to restart that level.
* AntiClimaxBoss:
** The bosses with playable characters and the first few E-Series battles have particularly slow AI and can be defeated before they even so much as make a proper attack. Knuckles' battle in particular is memetic for this combined with [[DullSurprise how casually he reacts to getting hit.]]
** For as much of an ImplacableMan ZERO is in Amy's stages, the actual boss fight against him is pretty easy. All you have to do is hit the robot into the electric fence surrounding the arena and hit the button that is revealed by doing so, which can be done in under a minute.
** Big's only boss encounter can be beaten in under 30 seconds, as the only thing you're required to do is literally fish Froggy out from Chaos 6. It's less a fight and more another fishing mission where your (hostile) lake is moving towards you.
* AssPull:
** The concept of the Chaos Emeralds having both positive and negative energy isn't brought up until just before the final battle of the game. Just when everything seemed lost with Perfect Chaos absorbing the remaining of the energy, Sonic's friends pop up and tell him that Chaos actually only took the negative energy of the emeralds, and that he could still use their true power with ThePowerOfFriendship. While there was meant to be foreshadowing to this revelation with Tikal's prayer "The servers are the 7 Chaos. Chaos is power... Power enriched by the heart. The controller is the one that unifies the Chaos.", the wording ended up too vague to what it was referring to, resulting in the penultimate scene coming off as a [[EleventhHourSuperpower convenient way]] of letting Sonic become Super Sonic and get the edge over Perfect Chaos.
** Eggman pulling out a second Egg Carrier he just had lying around to fight Perfect Chaos, because he "thought something like that could happen".
* [[Awesome/VideoGameLevels Awesome Video Game Levels]]:
** [[PalmtreePanic Emerald Coast]] is a phenomenal introduction to Sonic in 3D with its multiple pathways, shortcuts, smooth act transitions, relaxing music, and [[SignatureScene the iconic orca chase sequence]].
** [[SlippySlideyIceWorld Icecap]] returns, and is once again a wintry playground with plenty of ways to blast through the level and an ''epic'' snowboarding sequence at the end, where Sonic and Tails race against an entire avalanche… [[SugarWiki/MomentOfAwesome and win]].
** [[AmusementParkOfDoom Twinkle Park]] opens with a kart race, leading into a high-speed roller coaster ride to a colorful area with a plethora of different paths, fun ten pin bowling mini-sections, and a cheery soundtrack.
** [[MetropolisLevel Speed Highway]] is the game's most famous level by far, and for good reason. The entire zone is focused on maintaining Sonic's momentum as he plows through Badniks, runs down the sides of buildings, and crashes through windows to outrun Eggman's forces.
* BaseBreakingCharacter: Big the Cat started out as TheScrappy for a great many people, and not just because of his levels. However, he has garnered a plausible fanbase over the years to balance it, especially following his appearances in later games. While many still think his gameplay was executed poorly, some still appreciate his role as a more divergent laid back Sonic character.
* BigLippedAlligatorMoment:
** After the Tornado is shot down, Sonic crashes on Emerald Coast, stands back up and wonders out loud about what happened to Tails. A little girl is standing next to him as this happens, just staring curiously. In the Japanese script, Sonic doesn't even acknowledge her. The camera focuses on the still silent girl watching Sonic run off, and then she isn't seen ever again.
** In Tails' Story: Tails running into Big the Cat while carrying the Chaos emerald infected Froggy counts as such, as Big crashes on the ground, Froggy escapes, Big moans about losing his friend again and leaves. This leaves Tails giving a LampshadeHanging wondering what just happened and it's never spoken of again.
* BrokenBase:
** The "alternate gameplay." Unlike the earlier ''VideoGame/Sonic3AndKnuckles'', each character has their own goals and dedicated levels as opposed to playing essentially the same with a unique ability. Some love this for making the characters feel truly unique instead of "slower Sonic with X ability", while others dislike it for being disruptive to the game's overall flow. There's also a camp that believes that the alternate gameplay in this game is better handled than in the succeeding games, as while this game allows you to play through a single character's story all the way through, some later games force you to switch characters in the same story. Specific issues are:
*** Tails' stages are either loved for their freedom of movement and high-speed gameplay, while detractors decry the stages for how the levels are blatantly recycled portions' of Sonic's stages, with the stages being too [[ItsShortSoItSucks short]] and [[ItsEasySoItSucks easy]] to be compelling.
*** Amy's gameplay is either seen as a nice change of pace from the fast-paced gameplay of Sonic or a slow, generic platformer with awkward puzzles.
*** Gamma's gameplay is either a destructive romp through hordes of Eggman's robots or an overly simplified or repetitive shooter.
** The 2003 UpdatedRerelease ''Sonic Adventure DX'', while functional, is quite a mixed bag of a port, and there is a good amount of infighting regarding its quality and how it fares compared to the original game. Some decry the port and feel it completely ruins the original game and its atmosphere due to the changed visuals, the admittedly inferior presentation (simpler lighting compared to the original's more complex lighting, compressed and removed audio clips, etc.), and bugs not found in the original game.\\\
Others, however, argue that the numerous improvements from the original game -- improved loading times, smoother framerate, updated models, and additional content (such as the unlockable Game Gear games and a mission mode) -- more than make up for its technical shortcomings and that they aren't enough to truly ruin the game and/or devalue the port entirely. Even those additions are controversial; the framerate isn't entirely consistent and breaks some elements that were based on the original's locked 30 FPS, and the mission mode can feel like a lot of FakeLongevity with little original content of its own.\\\
The one thing that ''DX'' is universally agreed to be good for is [[GameMod modding]], since a plethora of mods have been created for the game's PC release to patch the bugs and bring it up to modern standards, while adding the option to revert the more controversial changes for a "best of both worlds" experience.
** Should it get a remake? In light of [[https://www.sonicstadium.org/2018/12/takashi-iizuka-is-really-interested-in-remaking-sonic-adventure/ Takashi Iizuka expressing interest]] in doing a remake, there is debate amongst the fandom on how or if ''Adventure'' should be remade. Some argue that a remake would do wonders for the game given how poorly aged aspects of it are and remaking it would allow Creator/SonicTeam to fix a lot of the game's presentation and gameplay issues. Others however, felt the game is much too flawed and [[ContestedSequel divisive]] for a remake to truly please fans and/or critics and argue that Sonic Team is better off using it's good ideas for new ''Sonic'' titles instead. There's also a third group that aren't against the idea, but don't trust the current Sonic Team to pull it off successfully and argue that it'll be better off in the hands of a seperate developer instead.
* CameraScrew: The game is known for having a capricious and difficult to control camera system that frequently snags on the geometry of levels, though ''DX'' slightly remedied it through adding the free camera option. It infamously started the trend of 3D Sonic games having subpar camera systems.
* CharacterRerailment: According to Creator/YujiNaka, Sonic was specifically redesigned in this game to look more like a "bad boy" in order to emphasize [[MascotWithAttitude his intended personality]], after having drifted into more of a cutesy character in the preceding years. While his lax attitude ("I don't show off, don't criticize") may seem at odds with both previous American depictions and later games, it's closer to how he was originally described in Japanese sources.
* ClicheStorm: Gamma's entire story arc is a dime-a-dozen "{{Ronin}} Samurai who turns against his master to strike out on his own" story [[JustForFun/RecycledInSpace retold in the form of a robot foot-soldier]]. Notably, his story arc was deliberately [[LeftHanging left unfinished]] in the [[ComicBook/SonicTheHedgehogArchieComics Archie comic adaptation]] specifically because the writers realized that his story was [[https://web.archive.org/web/20101130224808/http://www.teamartail.com/archie/reviews/sss13.html "something you've seen a hundred times if you're a devotee of samurai movies".]] It does lessen this by playing off as a clever and tragic {{deconstruction}} of the franchise's badnik lore, and also by being a much less common story trope outside of Japan.
* ComeForTheGameStayForTheMods; The Steam release is generally considered a PortingDisaster due to having downgraded visuals and additional bugs, thanks to being a port several consoles removed from the original release. This version, however, is the most ideal for modding. A mod called "Dreamcast Conversion" returns the game to its original state by reverting the visuals and fixing the bugs, while other mods such as "[=BetterSADX=]" include extra upgrades like running at proper 60 FPS in full widescreen, restoring the Dreamcast version's DownloadableContent, and adding extra features like [[SuperMode Super Sonic]] and new levels. These mods create what is considered to be the definitive version.
* CommonKnowledge: It's not unheard of for this game to be claimed as an explanation of Knuckles' backstory, but the tragedy it depicts happened thousands of years before his time--how Knuckles came to be the Master Emerald's guardian is still a RiddleForTheAges. Admittedly, this is not at all helped by how the game misleadingly {{Bookends}} Knuckles' story with the Echidna pondering why he's become the guardian, [[RedHerring which clearly implies Tikal's backstory is the answer]].
* ComplacentGamingSyndrome: When it comes to raising Chao, players usually stick with the Station Square garden, which is the first one unlocked and the simplest in design. The Mystic Ruins and Egg Carrier gardens are much less conventional, harder to navigate, and lack access to the Chao Stadium (and, in ''DX'', the Black Market).
* ContinuityLockout: No mention of Super Sonic is made prior to his appearance in his own story. While you'd know that Sonic has a SuperMode if you played prior games, if you haven't, then it comes across as a DeusExMachina.
* ContestedSequel: This was Sonic's first leap into 3D, and as a result the game is looked at as either a successful transition or a pretty shaky flop. Common points of praise include the great graphics (which put many competitors to shame during its release), strong RashomonStyle plot, general presentation upgrades like deeper storytelling and voice acting, as well as having some of the best levels in the entire series. Points of contention include the game's buggy nature, its issues with pacing, and the overall "serious" tone clashing with older Sonic titles. Also included are the game's alternate gameplay styles for its other characters, who are either seen as strong improvements to the Sonic formula and unique differentiations from the series' traditional gameplay, or odd and offputting deviations from playing as Sonic himself.
* DifficultySpike: Gamma's campaign, for the most part, is just shooting its way through short sections of Sonic's levels. There is a timer, but most players won't even notice it because of how quickly they go by. Hot Shelter, however, is a massive step up from every level before it. It's much longer, and has a tricky train ride section that can eat up a lot of time. It's common for players to be in for a shock when they actually get timed out partway through the level.
* EnjoyTheStorySkipTheGame: Gamma's story is not only considered the best of the playable characters (with a fair number of fans even saying it's better than the overarching plot of this game) but remains one of the most beloved stories in the entire ''Sonic'' franchise. His gameplay on the other hand, tends to be as divisive as the other non-Sonic playstyles.
* EnsembleDarkhorse: Tikal, the resident ExpositionFairy. Her fanbase is relatively strong and enduring for what is essentially an one-shot character (not counting her multitude of cameos) and some fans even tend to have her be part of Sonic's friend circle in their fanworks.
* EsotericHappyEnding:
** During the OmegaEnding, the TrueFinalBoss gets a HappyEnding despite having committed mass murder against countless innocent lives and razing Station Square nearly to the ground.
** Even better in [[DubInducedPlotHole the English version]], where Tails responds to the end of the crisis with, "All's well that ends well," even though the city is still in ruins.
* FairForItsDay: While Amy is a [[PinkMeansFeminine pink girl]] in love with the main hero, and still has her StalkerWithACrush traits that would be {{Flanderized}} in the 2000's, she was still a fully-playable heroine with her own story at a time when this was rare for a PlatformGame, and her story's end goal is independent from Sonic (who is technically a side character in her route). TheNew20s saw several video essays from women gamers who found Amy's playable status inspiring when they were kids.
* FanPreferredCutContent: While the final incarnation of Windy Valley is by no means hated, many fans tend to prefer the zone's [[https://youtu.be/3YhS4nhs8fM first incarnation]] (which was discovered via a leaked demo in 2013 after years of speculation and was then promptly restored by the modding community not too long after) over its final incarnation. Largely due to it being far larger and more open-ended in the vein of the 16-bit Genesis games. Some have even called it the best stage in the game and the ideal 3D Sonic stage for that reason alone.
* FanficFuel:
** The mysterious grey Mecha Sonic in Final Egg (or Silver Sonic v2.0 as referred to by the [[ComicBook/SonicTheHedgehogArchieComics Archie comics]]) has been the source of much speculation by fans, with numerous fanworks featuring the mecha as an opponent or exploring it more in depth.
** Many Tikal-centric fics tend to explore her past and friendship with Chaos prior to the Echidna tribe's attempt to seize the Emeralds in greater depth.
* {{Fanon}}: The tornado in Windy Valley is merely a video game obstacle that none of the characters are shown reacting to, but fans tend to interpret it as [[https://www.youtube.com/watch?v=kSjzsWv6lwM Sonic willingly jumping in as a thrill ride.]]
* FranchiseOriginalSin: See the [[FranchiseOriginalSin/SonicTheHedgehog franchise page]].
* GameBreaker:
** Tails' flying speed upgrade, the Jet Anklet, makes Tails faster than ''Sonic'' when he flies! The upgrade makes Windy Valley a joke and makes the rest of the game noticeably easier... when you're not wrestling with the camera, anyways. It's also one of the only upgrades you can get as soon as the intro ends, as once you know where it is[[note]]Inside a hidden room above the Sewage Maintenance pool behind Twinkle Park, which can only be accessed by flying upward[[/note]], there is literally nothing stopping you from getting it.
** Tails' flight in general. Compared to other 3D Sonic games, this one has easily the most overpowered flight ability. Tails gets a lot of height and distance, moves quickly, and goes even further and faster with the Jet Anklet. He can slowly descend to the ground or quickly dive down. There's no real height or distance cap beyond your momentum and flight stamina, which only drains while you're holding the jump button. Case in point: [[https://www.youtube.com/watch?v=8DLzQfLBw-w Tails can skip the entirety of Windy Valley by just descending]] if you know where the death zones are.
* GameBreakingBug:
** It's possible to glitch Knuckles into Casinopolis early, or glitch into Sky Deck before witnessing the Egg Carrier transformation sequence. If either glitch is performed and the player goes on to complete the level, Knuckles will be transported to the past as usual, but the cutscene with Tikal will not trigger, meaning he's stuck there permanently. Quitting and reloading will not fix this, as the game will autosave at this point, meaning the only way to fix it is to delete the file and start over from the beginning. A similar glitch can also happen with Big if the player glitches into the hotel and completes Emerald Coast without completing Ice Cap.
** As Sonic, it's possible to do a precise spindash jump and clip through a wall to access the Angel Island area as early as his first visit to Mystic Ruins. Doing so allows the player to obtain the Ancient Light and play Red Mountain much earlier than intended. However, if they actually ''complete'' the level, they will be forced directly into Sky Chase Act 2 and end up on the Egg Carrier. There ''is'' a way to escape, but the player will eventually be forced to play Red Mountain and Sky Chase Act 2 when they normally would, leaving Sonic trapped on the Egg Carrier for good with no way to continue the story at that point.
* GoddamnedBoss: Chaos 4. Most of the time he just swims around his arena, sinking lilypads and throwing splash attacks at you, none of which actually deal damage. In fact, the only move he has that actually deals damage (aside from you running into him) is a highly telegraphed and easily avoided shockwave attack. He's one of the easiest bosses in the entire game, yet whenever he's underwater he's also invincible, meaning you spend long periods of time jumping around the arena simply waiting for him to resurface so you can hit him. It takes a total of five hits to down him and you usually need to wait a minimum of 15 seconds between attacks. Oh, and he's also tied for the most common boss in the game, as you have to fight him with three different characters (Sonic, Tails, and Knuckles).
* GoodBadBugs:
** Using glitches will let you finish Casinopolis in [[https://www.youtube.com/watch?v=jM8OHF--aa0 seven seconds]].
** Some glitches in the game allow characters to enter usually inaccessible areas or play around with unused content in the game. For example, there is a glitch method for nearly every character to get into Sonic's Emerald Coast. Do be warned some of them have the potential of screwing up gameplay or save data.
** It's possible to glitch into Speed Highway early with Sonic and Tails by going through Knuckles' entrance, which causes some minor visual bugs at the point where they would normally play it (mainly the missile cutscene with Tails taking place at night rather than sunset).
** Possibly not a bug, but if you use the Light Speed Attack (as Sonic) or Maximum Heat (as Knuckles) when fighting Chaos 6, it'll do double the damage and you can beat the boss in under a minute.
** With Sonic, if you Spin Dash at the right angle and time your jump correctly in the sand cavern in the Mystic Ruins' jungle, you can get to the normally out-of-reach button to drain the sand out, allowing him to access the Sand Hill mini-game via the map like you would normally do with Tails. Both of them have unique idle dialogue for the level, suggesting it was originally a regular level that got demoted to a mini-game.
** It's possible to use one animal on the same Chao repeatedly by placing the animal in front of it and picking it back up, rather than giving it directly to the Chao. This saves a lot of time searching for animals in the Action Stages, and it's basically the only viable method of getting your Chao to max stats.
** A debug feature for the Egg Walker fight was left in the Dreamcast version. Pressing the Y button causes the boss to change its behavior.
** Also exclusive to the Dreamcast version: if you play through the whole game without loading a save file, [[https://www.youtube.com/watch?v=mD98Rh36yYI Big loads Amy's textures]] in Super Sonic's story.
* HarsherInHindsight: Chaos's retaliation against the echidna tribe's attack on the chao becomes a lot worse when ''Frontiers'' reveals [[spoiler: Chaos's ancestors, the Ancients, were wiped out by The END for extremely petty reasons; namely, it was pissed off they thought they could flee to avoid it. Then the echidna tribe proceeds to do the ''exact same thing'' by killing all of Chaos's chao friends and mortally wounding Tikal purely out of desire for power, retriggering the trauma he experienced after the loss of his people]]. No ''wonder'' why Chaos was so pissed.
* HeartwarmingInHindsight:
** Sonic's ImageSong, ''It Doesn't Matter'', is SugarWiki/AwesomeMusic, but the lyrics don't particularly reflect his actions in this game since he's fully a confident, cocky StockShonenHero while the song implies he's uncertain about the right thing to do, but doesn't let that stop him from enjoying life. Here, it seems more like an extra insight into his personality. However, it does reflect his words and actions in the ''VideoGame/SonicStorybookSeries,'' where he admits he doesn't mind playing the bad guy once in a while and even when stating [[AnAesop the moral of]] ''VideoGame/SonicAndTheBlackKnight,'' to live life to the fullest while you still can, he ends with "At least, that's what I figure." To drive the point home, the game even reprises ''It Doesn't Matter'' for the climax.
** ''VideoGame/SonicFrontiers'' would have Chaos's ancestors be avenged when Sonic fights and defeats [[spoiler:The End]], the whole reason why the Chaos Emeralds came to Sonic's world in the first place.
** Sonic helping Big, a complete stranger whom he's never seen before, get Froggy back from Chaos 6 becomes even more heartwarming when ''VideoGame/SonicFrontiers'' has Big appear in Cyberspace as part of Sonic's memories because of this exact interaction, meaning Sonic never forgot him, and he took the time to not only learn Big's name, but also to learn and enjoy Big's favorite hobby to wind down.
* HilariousInHindsight:
** The reason why Chaos is made out of water was to show off the graphic capabilities of the Sega Dreamcast compared to the previous generation's hardware. Morpha from ''VideoGame/TheLegendOfZeldaOcarinaOfTime'' beat them to the punch by a month, being a water monster on the weaker Nintendo 64, though it obviously isn't as complex as Chaos.
** This game has a level named [[TempleOfDoom Lost World]]. Then 15 years later, we got ''VideoGame/SonicLostWorld''. Not only that, but the first section of the Windy Valley level is called Windy Hill, which is the first level of ''Lost World''. The Lost World stage itself features a tunnel section and a wall running section reminiscent of features that would become a staple of the Lost World game.
** The first four Chao Races are the Pearl, Amethyst, Sapphire and Ruby Courses. ''WesternAnimation/StevenUniverse'' fans will get a chuckle out of it, since these four gems are three of the main characters. Also, three of these four are installments of the ''Franchise/{{Pokemon}}'' series.
** Chaos 2 is the only form of Chaos that Sonic doesn't get to fight (Knuckles fights it instead). Less than a year after ''Adventure''[='=]s release, ''Series/RobotWars'' Series 3 began in the UK and was won by a robot named Chaos 2. The name of its second opponent? ''Sonic.''
** Eggman criticising the Black Arms' wanton destruction of Westopolis in ''VideoGame/ShadowTheHedgehog'' (because he can't turn it into Eggmanland if it's not there) rings ''very'' hollow when you remember that in this game, destroying Station Square and building Robotnikland atop its ruins was his ''entire goal''.
** Eggman said "It's no use" long before [[VideoGame/SonicTheHedgehog2006 Silver]] made it a meme.
** During Gamma's story, Eggman gathers all of his E-100 robots (sans Zero and Beta) together to [[LetsPlay/SnapCube "hear a very special announcement"]].
** ''VideoGame/SuperMarioOdyssey'' features a world which eerily resembles Station Square, complete with realistically rendered humans. And if that and the use of a lyrical pop vocal track as the game's main theme wasn't enough, the ending of that game [[spoiler:has an escape sequence with a [[ThemeMusicPowerUp rocking vocal song reminiscent of Crush 40's tracks]]. The music is even sung by Tails' later voice actor, Creator/KateHiggins.]]
** One poster made to promote the Director's Cut was inspired by the film ''Film/{{Speed}}''. Fast forward to ''Film/SonicTheHedgehog2020'', and Sonic's favorite film is ''Speed'' itself!
** Many jokes have been made about ''Anime/LoveLive'' music sounding like ''Sonic'' music, but ''Anime/LoveLiveSunshine's'' "WATER BLUE NEW WORLD" stands out for sharing a similar name with Emerald Coast's first track, "Azure Blue World."
** Take a look at [[https://sonic.fandom.com/wiki/Chao Chao]]. Now take a look at the ''Franchise/{{Pokemon}}'' [[https://bulbapedia.bulbagarden.net/wiki/Manaphy_(Pokémon) Manaphy]]. Bonus points for both of them being [[MakingASplash Water-type]].
** A Sega hero enters a casino with his allies (one of which is a fox) in order to steal a treasure by playing the casino’s games in order to win a currency used to make a path to the treasure, only to fail at the last moment and be forcibly drugged. Did we just describe Casinopolis or the casino palace in ''VideoGame/Persona5''?
** This game features a very large PowerGem with the ability to control an amorphous evil entity that is shattered at the start of the story. It also features a hero who, guided both by a friendly spirit and by the jewel itself, must collect all the shards of this jewel--three per level--to restore the jewel to its original state. It's Knuckles [[VideoGame/Kirby64TheCrystalShards 64: The Crystal Shards]]!
* InferredHolocaust: Station Square is completely destroyed in the final battle, and is shown to be quite populated right before Perfect Chaos floods the city. Unless everyone somehow evacuated in an impossible amount of time, tons of people would have drowned. The ''Anime/SonicX'' adaptation [[NoEndorHolocaust addressed this]] by showing that everybody evacuated in time and the city was repaired shortly afterward.
* IronWoobie: Despite how [[WhatMeasureIsAMook neglected it was by everyone except Amy]] and everything it went through, E-102 Gamma doesn't angst about any of it.
* ItsEasySoItSucks: A recurring complaint towards some of the alternate character missions is that a lot of their levels are just truncated versions of Sonic's and are patronisingly simple to get through for the large part. Tails and Gamma suffer most frequently from this. As mentioned above, many of the bosses don't have particularly intelligent AI either and can be defeated in a matter of seconds
* ItsTheSameNowItSucks: ''Sonic Adventure'' reviewed quite positively during its initial release on the Dreamcast, as did [[VideoGame/SonicAdventure2 its sequel]], and the UpdatedReRelease of said sequel for the [=GameCube=]. Sega went ahead and similarly re-released ''Sonic Adventure'' as ''Sonic Adventure DX''. Despite being a faithful port that significantly touched up the graphics, fixed a lot of the glitches, and added a whole new gameplay mode and bonus character, ''DX'' received middling-to-negative reviews from most gaming publications, often times scoring several points lower than the reviews of the Dreamcast version of the game by the same publication. It got even worse when the HD port was released- some reviewers ended up rating it lower than ''VideoGame/SonicTheHedgehog2006''. Part of this can be attributed to the fact that ''DX'' was released in 2003 (over four years after the original) and platform games in general had experienced many new advancements in the interim, making the game look somewhat dated despite the graphical enhancements. It didn't help that, despite the new extra modes, its "Director's Cut" moniker was fairly superficial, with ''DX'' doing very little to polish up the blatantly unfinished elements of the original game, and [[https://dreamcastify.unreliable.network actually made many things worse,]] particularly regarding transparency and lighting.
* JustHereForGodzilla: While the other playstyles (except for Big's) have their fans, many have bought the game simply for Sonic's gameplay. This would become a trend for future 3D releases, to the point of criticism.
* MagnificentBastard: [[Characters/SonicTheHedgehogDrIvoEggmanRobotnik Dr. Ivo "Eggman" Robotnik]]'s objective in this game is to destroy Station Square in order to build his own city, Robotnikland. To do so, he freed Chaos and turned him into his ally. Since Chaos grows stronger by absorbing the Chaos Emeralds (and would eventually destroy Station Square once he has all seven), he decides to collect them. As such, he attacks Sonic and Tails to steal their Chaos Emerald. Despite his defeat, he succeeds in stealing the Emerald when they are distracted. He then revealed to them his plan, [[BatmanGambit expecting them]] to collect the Emeralds before him, which would allow him to easily steal them. While his plan works, he also collect two emeralds by himself, obtaining 6 Emeralds. When Chaos 6 is defeated by Sonic and Knuckles, Eggman fires a missile at Station Square, only falling because of the missile malfunctioning and Tails' interference. [[BewareTheSillyOnes Despite his silly, over-the-top attitude]], Eggman remained constantly a step ahead of the heroes for half of the story, reminding you why he's Sonic's [[ArchEnemy archnemesis]].
* MemeticMutation: The game has spawned several memes in and out of the ''Sonic'' fanbase, including:
** ↑ & ↓ & ↻ ("Up and down and all around"), [[SugarWiki/AwesomeMusic thanks to the sampling in Speed Highway]].
** "You're gonna crash, ah!" [[note]]An infamous line delivered by Sonic early in the game when he sees Tails' plane crash. The utterly wooden delivery of the line, combined with Sonic's ridiculous facial expression, has made it a classic meme.[[/note]]
** "Oh no", delivered in monotone by Sonic or Knuckles during their character fight scenes. Mostly the latter, especially how {{Narm}}y it is. What's even more funny? It's originally from [[https://www.youtube.com/watch?v=7FPEtz-rC5s a beta version of the game]] specifically his reaction when he realizes that Angel Island is going to fall into the ocean after Chaos broke out of the Master Emerald, and yet, it ended up still being used for the character fights with him. There's also an extended version of the meme that invokes his line before the last hit, "Give it your best shot!" It's likely a player will finish him off before he gets to finish his line, so instead it becomes "[[InterruptingMeme Give it your best...Oh no.]]"
** [[LargeHam GET A LOAD OF THIS!]] [[note]]A very popular, over-the-top line Eggman spouts repeatedly during the Egg Viper and Egg Walker fights.[[/note]]
** The first verse of "Unknown From M.E.", particularly the lyric "Unlike Sonic, I don't chuckle".
*** "Knock Knock it's Knuckles". Even Creator/IdrisElba, Knuckles' voice actor for the ''Film/SonicTheHedgehog22022'' movie, [[https://twitter.com/idriselba/status/1425174698007138305 got in on the fun]].
** "Aw yeah! This is happening!"[[note]]Sonic's very first line in the game, popular for its exploitable nature.[[/note]]
*** NO, THIS ISN'T HAPPENIN'! [[labelnote:Explanation]][[https://www.youtube.com/watch?v=IBnq3fELuf8 A mod by SPEEPSHighway]] replaces Sonic's opening line with Zero's infamous dialogue from VideoGame/MegaManX4.[[/labelnote]]
** "The Sphinx looked so cute, I had to shave it" [[note]]A line from Amy's theme "My Sweet Passion", which comes off as uncomfortably sensual to many[[/note]]
** Sonic's early redesigned design from before they smoothed it out in future games, with his lanky, noodle-like limbs and DreamworksFace, is frequently poked fun at and referenced amongst fans.
** "Something bugging you?" Yes, Sonic's DerangedAnimation [[https://www.youtube.com/watch?v=wCBYDBo9t6E when saying the line.]]
** The iconic [[https://i.kym-cdn.com/entries/icons/mobile/000/025/976/thumb.jpg "Sonic doing a finger gun while spinning" pose]] on the game's box art has been replicated and parodied with numerous other characters in fan art and other media; including the [[https://www.destructoid.com/wp-content/uploads/2021/01/616148-Scott-Pilgrim-Switch-physical-version-Limited-Run-Games.jpg alternate Limited Run covers]] for ''VideoGame/ScottPilgrimVsTheWorldTheGame''.
* MoralEventHorizon:
** The Echidnas [[spoiler:trampling and killing the poor Chao standing in their way just to get to the Chaos Emeralds and the Master Emerald. They didn't have qualms about taking down Tikal either (she wasn't killed though); even her ''father'' Pachacamac didn't care, just as long as they seized the Emeralds]]. This wasn't a very good idea.
** Eggman, after his Egg Carrier sinks and his Chaos plan is foiled, crosses it when he decides to launch a ''nuke'' on Station Square purely out of spite.
* {{Narm}}:
** The drowning audio. Special mention goes to the audio used for Knuckles -- not only does he end up sounding like he's been possessed by WesternAnimation/{{Goofy}}, but it's used as part of a (mostly) serious [[https://www.youtube.com/watch?v=af8eUGJGT-0 cutscene]] near the end of his game. Above water. It almost sounds like he's choking on his own tongue.
** Speaking of Knuckles, his theme song's claim that he 'doesn't chuckle' has often been made fun of by fans due to remembering him chuckling quite often in ''VideoGame/Sonic3AndKnuckles''.
** One of the final shots of Super Sonic's story in the English dub is Tails saying "All's well that ends well" - while standing on a collapsed highway in a decimated Station Square. This is a bit of dub-exclusive Narm, given that the original Japanese has Tails merely expressing relief that Chaos' rampage is finally over.
** The out of nowhere reveal that Sonic is singing at the end of his story is a lot funnier than intended.
** Knuckles' fight with Sonic and Tails, which could have been more dramatic and important--given that it features prominently in no less than three character stories and is an essential stepping-stone on the road to Perfect Chaos--but is completely deflated by the fact that it's a purely gratuitous butting of heads that requires everyone involved to dance around obvious solutions and refuse to ask or answer clarifying questions. The awkward sound quality of the voices does not help.
** The stiff and clumsy animations, things like the fact that characters talk by having their mouth-parts grow and shrink, [[NarmCharm while they sometimes work despite themselves]], are nearly always silly and distracting.
** What should be one of the most important backstory cutscenes in the game is rather undermined by the fact that it's ''Big the Cat'' who is witnessing it, the character who is by far the ''least'' connected to the overarching plot.
* NarmCharm:
** Despite all the goofy qualities listed on this page, most fans will admit it has one of the best stories in the series. The acting may be a bit wooden and stiff, but generally the cast pulls things together enough when the moment requires it. Particularly Tikal's flashbacks, which still possess a haunting charm.
** The stiff robotic animation, for obvious reasons, has positive effect on E-102 Gamma's storyline. It helps that, due to his intentionally emotionless acting and design, his dialogue is the least hindered by corny execution.
** While the facial expressions are mostly just goofy, they're ''[[{{Moe}} adorable]]'' on [[KidSidekick Tails]] and [[GenkiGirl Amy]].
** The music fills in emotionally for the relatively primitive and often goofy 3D animation. Many of the scenes in the TearJerker section are accompanied by Event: Sadness for good reason.
* NauseaFuel: Failing to exit either pinball game in Casinopolis with more than 100 rings lands you in a sewer. Eww! And Tails has to race through it in his storyline.
-->'''Sonic:''' (''[[IdleAnimation while idling]]'') Ugh... this place smells like trash!
* NeverLiveItDown: Knuckles is mostly remembered for his {{Narm}}-filled fight scene with Sonic, despite his backstory being the driver of the game's entire plot. The game itself doesn't help matters since it glosses over his feelings towards his ancestors.
* ObviousBeta: The game was rushed for its original Japanese release after development for it was halted in order for it to be made for the Dreamcast instead, and was loaded with glitches, forcing Sonic Team to delay the U.S. release by a year to patch it up. Even then, the game still has loads of glitches, so it's very easy to break wide open, most notably in the ''DX'' port, which adds even more glitches than the original Dreamcast game. [[http://www.gamefaqs.com/pc/624155-sonic-adventure-dx-directors-cut-2011/faqs/26151 This page]] gives many examples of them.
* OlderThanTheyThink:
** This isn't the first time Eggman wears goggles. In one episode of ''WesternAnimation/SonicTheHedgehogSatAM'', Eggman (or Robotnik as he is referred to in that series) is seen wearing a [[https://i.ytimg.com/vi/ONCgrHoubAk/maxresdefault.jpg very similar pair of goggles]] to what he has in this game and all future Sonic games.
** This isn't the first game to feature Sonic and co. in 3D. ''VideoGame/SonicTheFighters'', ''VideoGame/ChristmasNights'', ''VideoGame/SonicJam'', and ''VideoGame/SonicR'' all predate it. In fairness, though, Sonic Adventure is the first ''mainline entry'' in 3D, while the aforementioned titles are, respectively, a FightingGame spinoff, a {{Tech Demo|Game}} bundled with a completely different game, a CompilationRerelease of the Genesis games with a 3D HubWorld, and a RacingGame spinoff.
** The game's backstory was alluded to in the [[AllThereInTheManual Japanese manuals]] for the classic trilogy. The manuals for [[https://info.sonicretro.org/Sonic_the_Hedgehog_2_(16-bit)/Manuals Sonic 2]] and [[http://info.sonicretro.org/Sonic_the_Hedgehog_3/Manuals Sonic 3]] both mentioned an ancient civilization which used the Chaos Emeralds for prosperity, but were wiped out when they tried to misuse those powers, and the Chaos Emeralds were then sealed away by the gods. That civilization turned out to be the Knuckles clan, and the god (as Eggman alluded to) was Chaos. Indeed, ''Sonic Adventure'' represents the developers finally having the technology to reveal this backstory in-game. However, because the Western audience had its own canon before the merger, on top of the Western releases often heavily simplifying the stories in the English manuals, many fans and critics felt the story came out of nowhere and was too drastic a tonal shift from the classic games, although enough of the backstory remained that it was still evident that the game expanded on ''Sonic 3''.
* OnceOriginalNowCommon:
** This game introduced a lot of things that would become clichés in the series like Robotnik getting upstaged or the Chaos Emeralds being used as an eleventh hour power-up. Thing is, at the time, this was all fairly revolutionary for the games (Robotnik had ''never'' been eclipsed as a threat by another villain), and a ''Sonic'' game containing CharacterDevelopment and a serious storyline was a very ambitious move for the series.
** Though it looks rather dated now, ''Sonic Adventure'' was designed to showcase the power of the Dreamcast in comparison to the Platform/PlayStation and Platform/Nintendo64 at the time, and it shows. Vast, highly detailed environments, advanced level architecture and other fancy effects for the time had multiple review publications saying that even PC games of the era didn't look as good as ''Sonic Adventure''. This was most obvious with Chaos, who featured numerous transparency and morphing effects which were ''impossible to accomplish'' on other systems. Underneath the hood, the original ''Sonic Adventure'' has a rather advanced [[https://dreamcastify.unreliable.network/index.php/lighting-downgrades/ palette lighting system]] that afforded the game a lot of atmosphere (keeping in mind that this was a time where most games didn't even ''have'' lighting engines). The DX port noticeably watered down the visuals, removing the lighting engine entirely, which makes its initial reception more understandable going back to the Dreamcast release.
** Another notable example is the game's in-engine cutscenes. At the time, cutscenes in games were usually limited to brief gameplay sequences, TalkingHeads, or PreRenderedGraphics -- see ''VideoGame/MetalGearSolid'' for a contemporary example. By contrast, ''Sonic Adventure''[='=]s cutscenes had sweeping cinematic camera angles, elaborate choreography, and dozens of character animations unique to them, all while lining up continuity-wise with the gameplay. While this was breaking new ground at the time, these cutscenes would look dated just a few years later, with games like ''VideoGame/MetalGearSolid2SonsOfLiberty'', ''VideoGame/GrandTheftAutoIII'', and even ''VideoGame/SonicAdventure2'' having fully-animated in-engine cutscenes that look much more cinematic than ''Sonic Adventure''[='s=] rudimentary showing.
* {{Padding}}:
** The game has you sit through the credits every time you complete each of the characters' campaigns, while you can skip it in the ''DX'' port, you will still be deprived the final completion emblems until you watch each of them in full.
** Amy's storyline consists solely of three short levels and a boss fight. The Dreamcast version tries to make up for this by making her adventure the most cutscene-heavy in the game (and unlike the DX port, you can't skip the cutscenes), but her story barely has any relevance to the main story, which makes her campaign's prolonged length even more egregious.
*** Both Sonic and Amy are sidetracked into completing a level that has no purpose in their story. Sonic enters Speed Highway to search for Amy only to find her getting kidnapped by ZERO in Station Square afterwards. Amy also enters Final Egg to search for Birdie's family, only to realize afterwards they are in the Egg Carrier instead. Both are fun enough levels, but seemingly only exist to bulk up either's campaign size.
** Big the Cat's stages don't rehash the other levels' layouts or gameplay styles, but at the same time, his gameplay is completely unorthodox, and his storyline has almost no bearing on the events of the rest of the game, giving the impression he was added to artificially lengthen the game. In fact, nobody in the entire game ever even learns his ''name'', making him seem even more out of place than he already is.
** A majority of Tails's story is essentially just a shorter version of Sonic's, with 4 of his 5 stages just being a small section of Sonic's with minimal changes. Most noticeably, Tails has to play both acts of Sky Chase and fight the Egg Hornet and Chaos 4, all with no changes whatsoever from Sonic's story.
** The first half of Sonic and Tails's stories involve playing a stage for a Chaos Emerald, then almost immediately losing it to Dr. Eggman afterwards. Casinopolis is particularly bad with this, with the duo getting ambushed by Eggman ''right after'' completing the stage, and proceed to lose the emerald they had just obtained a minute prior.
* PortingDisaster:
** The 2004 Windows port, though maintaining the extras of the [=GameCube=]'s ''DX'' port, is also marred with problems. It suffers from grainy-looking visuals, poorly re-sized HUD/UI elements, bad horizontal stretching, the game being prone to crashing when switching out to another window in fullscreen, keyboard controls can't be reconfigured, poor implementation of mouse controls (thankfully, they're optional), and poor optimization (at most, it will run at 30 FPS). The Chao system was heavily butchered as well -- there is no equivalent to the GBA's Tiny Chao Garden or the VMU's Chao Adventure, leaving the Chao Transporter's sole functions as naming and deleting Chao; while the removal of the Dreamcast version's breeding mechanics and the Tiny Chao Garden meant that every jewel-color Chao except for gold and silver, along with most colors that are obtainable by breeding jewel Chao with shiny Chao such as translucent Chao, were rendered unobtainable. In all versions of ''DX'', the Chao are generally unresponsive to being petted, the main way to increase happiness, and the only way to align them into Hero or Dark is with fruits bought from the Black Market, an expensive endeavor given how it's harder to earn rings in this game than it is in its sequel.
** The game was re-released in 2011 on Steam, based on the Xbox 360 port but introduced new problems such as the game's launcher not saving your settings, game running at locked resolution, poor frame-rate despite the Xbox 360 version being capable of running the game at 60 FPS, and the game is presented in a pillar-boxed 4:3 aspect-ratio. A patch was released in 2014 that fixes the issues with the game's launcher not saving settings, fixed the controls (keys are rebindable), better support for higher resolutions, V-Sync, and FXAA. However, the issue with the game's frame-rate remains unaddressed, it still runs in a pillar-boxed display, and despite supporting controllers, the analog triggers and D-Pad of an Xbox 360 controller do not work at all despite being based on the Xbox 360 version. With the Steam port of the game being based on the Xbox 360 and [=PlayStation=] 3 versions, this means the Steam port of the game is ''a port of a port of a port of a port.'' With each one usually getting worse visually. (Most of the gameplay issues came from the first port.)
* ScrappyMechanic:
** While most of the alternate playstyles fall under BrokenBase, Big the Cat's fishing stages are rarely defended due to not gelling with the rest of the game. The fishing mechanics themselves are also generally just seen as bad. If you jiggle the control stick even slightly the wrong way, you don't get the fish on the hook, you move the line the wrong way, and you have to reel it in exactly right or it will just magically get off the hook, at minimum stress, when it's ''right next to you''. What's worse is if your line breaks, you ''lose a life!''
** Nuts in the Chao Garden have to ripen in real time. Sure, there may be one extra fruit for each garden than there are in the sequel's gardens, but they also take a hell of a lot longer to grow. Have fun grinding rings for the Black Market fruits and listening to the constant complaining of your Chao's stomachs!
** Chao have a hidden life points stat in the original version of the game. If you hurt them (which happens to be ''very'' easy to do on accident) they'll lose life, which will trigger premature death if it runs out. Losing a fight in the VMU's Chao Adventure app can also prove to be fatal as well at times. Hope you've got a ton of spare nuts lying around.
** Removing a Chao's animal parts is extremely tedious due to the lack of Chaos Drives and skeleton dogs, things that are exclusive to ''Sonic Adventure 2''. The former boosts a single stat without replacing body parts, and the latter returns body parts to their normal appearances. If you're unable to use the Tiny Chao Garden to transport a Chao to ''Sonic Adventure 2 Battle'', either due to not playing ''DX'' on the [=GameCube=] or playing the Dreamcast or console/PC versions, you'll need a specific combination of animals and a lot of luck in order to clear a Chao of all of its animal features, which will probably have the side effect of altering its evolution due to the plethora of stats being influenced.
* SidetrackedByTheGoldSaucer:
** The Chao Gardens are a surprisingly complicated, very cute VirtualPet simulator that could work as its own game. The Chao racing and the way you have to go into levels to collect animals to enhance your Chao really extends the gameplay.
** Running around the adventure fields. Despite, or perhaps because they are harmless fields, it is really easy to get distracted exploring them. Keep in mind the game came out three years before ''VideoGame/GrandTheftAutoIII'' when WideOpenSandbox really blew up, so the fields were a novelty.[[note]]Compare running around Peach's Castle in ''VideoGame/SuperMario64''[[/note]]. The music helps too.
** The pinball machines in Casinopolis are nice distractions, while also being a good way to grind rings.
* SignatureScene:
** The most well-known sequence from the game is Sonic being chased by an orca in the first stage, Emerald Coast. It serves as a very effective showcase for the game's cinematic tone and the Dreamcast's hardware power, and featured heavily in contemporary previews and marketing material; it's also been homaged many times in later games in the series, such as ''VideoGame/SonicTheHedgehog2006'' and ''VideoGame/SonicGenerations''.
** Station Square flooding with the rebirth of Perfect Chaos. While it's technically part of the last story, it also serves as the opening cutscene, with incredible animation for its time.
* {{Squick}}:
** Try talking to some of the people in Station Square while playing as Amy. Most of their dialogue is rather mundane, but some of them will not-so-subtly attempt to flirt with her. Most notably is the guy walking around in front of Casinopolis that straight up asks her out on a date to get a soda. Keep in mind that Amy is ''12 years old''. Even if she wasn't, there's still the fact that she's a pink cartoony hedgehog being asked out by a human man who looks decades older than her.
** On the topic of Amy, there's also the fact that the game will constantly show her panties to the player, and makes it extremely easy to look up her skirt in pretty much any situation without even trying. Heck, there's times where it seems as though they're ''trying'' to do this, as ''the very first thing you see'' when selecting her is an upskirt shot. Again, Amy is 12 years old.
* SoBadItsGood: While the game is generally still well-liked in the fandom, some of the more aged cutscene and animation quirks tend to be used as meme fodder. One particularly popular example is the "You're gonna crash, ah!" scene, where Sonic has a ridiculous facial expression mixed with a very wooden delivery of his line.
* SuspiciouslySimilarSong:
** [[https://www.youtube.com/watch?v=iP5VzAc3i-A Casinopolis' main theme]] sounds very similar to [[https://www.youtube.com/watch?v=IIBRJ0KnczM "Changing Keys"]], the ''Series/WheelOfFortune'' theme song.
** [[https://www.youtube.com/watch?v=HfgsT9aD2po The music for Chaos 6's boss battle]] features a riff that sounds a lot like the ''Series/MissionImpossible'' theme.
** [[https://youtu.be/oAxgIoHIxug Egg Carrier: A Song That Keeps Us on the Move]] sounds very close to [[https://youtu.be/cIkKLskRYN8 The Dragon Gave a Loud Scream]] from ''VideoGame/NightsIntoDreams'', albeit a little slower, making this an example from the same company. Similar style, instruments, and melody, same key, and both melodies even begin with a long E note!
* ThatOneSidequest:
** Try the Ski Slope Snowboarding missions (53 and 54) in the DX version's mission mode and you'll find it is very hard to not go crazy trying to beat them. To add insult to injury, you risk running into a bug that crashes the game if you save mission 53 as your last one.
*** Mission 53 requires you as Sonic to pass the line of rings using the 3 jump ramps found near the end of Ice Cap. Mistime a single jump and you'll have to start over.
*** Mission 54 as Tails on the other hand requires you to grab 13 flags while racing Sonic. Due to the controls of the snowboard and the uneven terrain, it can be quite easy to miss them if you're not careful.
** Mission 58 has you running from the boulder in the Lost World. The catch? You have to collect twenty-something flags in the process. Not bad on its own, but [[EventObscuringCamera the camera makes it impossible to get the flags on the first shot]] because it's looking at the boulder instead of in front of you, and if you go too slow and get hit by the boulder, you'll miss two to three patches of flags for your trouble. Did we mention you had to get every single one? It ''is'' made an absolute joke if you can manage to spin dash under the boulder after triggering it.
*** You can also run to the end, wait for the boulder to fall down the pit, then jump back and run up the ramp, collecting the flags on your way up.
** Some of Sonic's A-Rank levels are horrendous, and the first level (Emerald Coast) is a prime example. It's a fairly straightforward level to run through on the C and B levels (finish the level and finish with 50 rings, respectively). For the A-Rank, though, you have only ''two minutes'', forcing one to spindash almost nonstop through the entire level while taking all of the stage's normal shortcuts (as in the ones the developers wanted you to take, not GameBreaker shortcuts found by speedrunners). It gets worse with levels like Red Mountain and Lost World, to name a few.
** Knuckles' A missions are just as bad, requiring the player to find all of the Master Emerald shards ''in under a minute'', which can be a bit of a problem in levels like Red Mountain and Lost World. Sky Deck is at least merciful enough to give the player 2 minutes to find all of the Emerald shards, but the point still stands.[[note]]You can use SaveScumming to make this easier. If you restart, they will all remain in the same place, so you can locate one, restart, then dash to it to activate a checkpoint. Repeat for the other two.[[/note]]
** Big's A missions. Catch a 2000g fish and then catch Froggy. It doesn't sound hard, but there's pretty much only one fish that big in each level, and the fish you catch respawn. Doesn't help that the fishing mechanics can be buggy (see ScrappyMechanic). Thankfully, it can be made easier if you remember it's a dark blue shark you're looking after.
** The second emblem in Sky Chase Act 1, which requires earning a score of 8,000 points. Said score is ''extremely'' hard to achieve, thanks to the game not making it clear how to lock on or earn bonus points, and the general lack of areas to gain a large amount of points on before the level ends. It's very likely you will end up getting the second emblem in Act 2 (20,000 points) well before Act 1 without even trying.
* ThatOneLevel:
** Hot Shelter as Amy. It's not especially ''difficult'', but it's like the level equivalent of GoddamnedBats: [[MarathonLevel very long]] and full of [[ScrappyMechanic annoying mechanics]] like doors you have to open by twirling the analogue stick (which, if you have the PC version of SADX, means mashing the arrow keys in the correct order) and key hunts. Meanwhile, the robot Zero is chasing you and putting you under constant pressure the whole time. No wonder the developers gave it an A-Rank time of 6 minutes 30 seconds...
** For Sonic's side, Lost World is very long and arduous and can be especially difficult on a first play since much of the level consists of a series of puzzle-solving mazes that can be quite hard to figure out if you don't know what you're doing.
** The first two sections of Sky Deck with Sonic are also notorious for their very large number of BottomlessPits and collapsing platforms, not to mention all the guns shooting at you at the same time. Many players find it even harder than the final level of the game. That it suffers from the largest number of glitches and collision issues out of all the levels doesn't help either.
* TheyChangedItNowItSucks: ''DX''[='=]s visual changes (such as the updated models and a more realistic artstyle to make it more in line with the game's artwork and it's sequel, ''VideoGame/SonicAdventure2'') and the simpler lighting compared to the original game have not gone over entirely well with the fandom, as many felt they take away from and even ruin the original game's atmosphere.
* TheyWastedAPerfectlyGoodCharacter:
** For those that don't consider the alternate characters {{Scrappy Mechanic}}s, many complain that their story modes are too small and undeveloped compared to Sonic's. None of the five extra characters gets more than five levels (only half of Sonic's ten), and aside from Amy's Hot Shelter, all of them only play roughly half of each respective level (i.e. Tails only plays the first half of Speed Highway, while Knuckles plays the second half). Some even believe they should have been allowed onto Sonic's levels instead of being given their own goals and sections of levels. Amy gets hit by this harder than any other character due to the fact she has the least amount of levels totaling in at only three, plus one boss battle and a single mini-game, and fairly minimal activity to do in the Adventure Fields. Big, likewise, only gets four levels, two of which are in heavily condensed areas of Twinkle Park and Emerald Coast, plus a [[AntiClimaxBoss very easy]] final boss.
** Chaos 1 is given a character model, but lacks a boss fight. And since Eggman starts giving the Chaos Emeralds in pairs after Chaos 2, Chaos 3 and 5 are never shown.
* TheyWastedAPerfectlyGoodPlot:
** Concerning the end of Amy and Gamma's stories, which were located at the now-sunken Egg Carrier, there was a missed opportunity for the two to meet each other again and have Amy learn that one of birdie's siblings was inside Gamma all along, which would've made their [[TearJerker final moments together more poignant.]] (Notably, ''Anime/SonicX'' ''does'' [[AdaptationExpansion have Amy witness Gamma and Beta's final duel]])
** E-102 Gamma's story, while already decent, could have served as a more thorough VillainEpisode campaign that goes into focus about how Eggman set about his plans of enlisting Chaos and outdoing Sonic throughout the first half of the game. However, after its training run, a huge TimeSkip occurs in Gamma's campaign mode, with its only use in the main plot before its HeelFaceTurn being to collect Froggy and distract Sonic with a minor battle.
** The game deliberately cuts off a good angle for lore and CharacterDevelopment when Knuckles decides to abandon the question of his own past entirely at the end of his story route.
** A majority of Tails's story is essentially just Sonic's again, and his character development about wanting to become more independent only comes into play about 75% of the way into his story. Unfortunately, all this amounts to is one stage and a unique boss fight before his story ends, making the whole plot point seem rather rushed in.
* TrappedByMountainLions: Some of the side characters' quests are very barely connected to the main story. This makes Tikal teleporting them to her timeline seem a questionable resort:
** Amy's in particular barely relates to Chaos' arc outside the Emerald Birdie is holding in its locket for half the story (Chaos never appears or is even mentioned in her story). It does drive a large chunk of Sonic's story, but Amy herself is locked out of the loop for most of the game.
** Big's story involves Froggy's similarly limited connection, also holding an Emerald and for some reason possessed to carry Chaos' "tail". While he at least fights Chaos in his finale, his contribution to defeating him is far less significant than that of Sonic and Knuckles. On top of this, Big never even learns what Chaos is, the significance of his "lucky charm" (the chaos emerald Froggy swallowed), or why Dr. Eggman was so interested in capturing Froggy in the first place. He does drive part of the plot in the last story however.
** E-102 Gamma, despite serving Eggman, is only involved through collecting the two aforementioned Emeralds and a short obligatory fight with Sonic, otherwise outshone by Chaos as his top mook. His narrative becomes quite self-contained after he cuts ties with Eggman, spending the rest of the game in a mission "saving" its brethren who are even more disconnected from the main story, though it's generally considered compelling enough in its own right compared to the previous two examples.
* UnderusedGameMechanic: Most of the character upgrades are this, the worst offenders being Sonic's light speed attack, Tails' rhythm badge, and Amy's spin hammer attack.
* UnintentionallyUnsympathetic: Chaos. Slaughtering Pachacamac and the Echidna tribe for trampling over the lives of his Chao brethren in their lust for power is one thing, but flooding a town of completely unrelated people ''millennia'' after the fact is much harder to swallow, yet he's allowed to peacefully ascend to heaven with Tikal after leaving Station Square in ruins.
* WinBackTheCrowd: ''Adventure'' was made as this to pull the Sonic series, and by proxy Sega themselves, out of the [[AudienceAlienatingEra bad rut they had fallen into]] during the UsefulNotes/SegaSaturn years. It only partially worked; while it was one of the most popular games on the Dreamcast, and is still beloved by many fans today, it ultimately didn't prevent Sega from bowing out of the console market and becoming a third-party company. Though one could argue that things might be worse for Sega without the Dreamcast or this game.
* {{Woolseyism}}: Despite the aforementioned {{Narm}} plaguing the English script, it bothers to make different dialogue for each interpretation of the story (which the Japanese version only did sparsely in key scenes). This is especially effective in Tails' story, where Deem Bristow makes his performance as Eggman sound much more sinister and intimidating from the young fox's perspective ([[VillainousBreakdown especially in the final parts of the story]]).
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