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1[[quoteright:350:https://static.tvtropes.org/pmwiki/pub/images/sonic_adventure.png]]
2[[caption-width-right:350:''[[{{Tagline}} The Original Hero is Back!]]'']]
3
4->''Can't hold on much longer (But I will never let it go!)\
5I know it's a one-way track (Tell me now how long this'll last!)\
6I'm not gonna think this way (Nor will I count on others!)\
7Close my eyes and feel it burn (Now I see what I gotta do!)\
8Open your heart, it's gonna be alright!''
9-->-- '''Music/Crush40''', "Open Your Heart"
10
11The highest-selling title for the Platform/{{Dreamcast}}, ''Sonic Adventure'' is the first main game in the ''Franchise/SonicTheHedgehog'' franchise to feature [[VideoGame3DLeap full 3D gameplay]]. It was released in Japan on December 23rd, 1998, and was localized for North America, Europe and Australia between September-December of 1999.
12
13The game has an increased focus on story, with voice acted cutscenes telling a much more elaborate plot than previous games. Dr. Eggman shatters the Master Emerald and releases an ancient aquatic creature known as Chaos from its confinement. Though Chaos is weak and anemic in its current state, the Doctor aims to obtain the seven Chaos Emeralds to empower it to world-conquering levels. His actions draw the six playable characters to Station Square, where their adventures unfold in a RashomonStyle plot. Completing all of the stories unlocks a seventh, final story that wraps up the loose ends of the overarching plot.
14----
15[[AC:Playable Characters and their gameplay types:]]
16* '''Sonic the Hedgehog:''' A virtuous blue hedgehog capable of running at high speed. Sonic's gameplay style is the most reminiscent of the side-scrolling games: just get to the goal, which is sometimes an animal capsule like in the [[Platform/SegaGenesis Genesis/Mega Drive]] games, and sometimes a Chaos Emerald.
17* '''Miles "Tails" Prower:''' A two-tailed fox with an aptitude for building machines almost on par with Eggman's creations. Each stage pits the player against Sonic (and later Eggman) in a race to the goal. His levels are just a single section of Sonic's levels, which Tails must traverse by employing his flying ability.
18* '''Knuckles the Echidna:''' Last descendant of an ancient clan, and current guardian of the Master Emerald. With the Master Emerald shattered, its pieces are scattered across the land and Angel Island plummets from the sky. Knuckles takes it upon himself to track down the missing pieces and restore the Emerald; the goal of each stage is to collect three shards, using his SpiderSense to pinpoint their locations and his sharp knuckles to unearth them.
19* '''Amy Rose:''' A pink hedgehog who is mostly defined by her crush on Sonic. Her goal is to protect a bird whom she befriended so she can return it to its family. Amy must outrun [=ZERO=], an [[ImplacableMan implacable]] robot in pursuit of the bird, and climb a giant balloon that will carry them to safety. Amy is [[GlacierWaif not very agile, but carries a large mallet]] which she can use both to defend herself and pull off acrobatic maneuvers.
20* '''Big the Cat:''' A slow-witted, lazy, but warm-hearted fisherman. After his pal Froggy swallows Big's "lucky charm"--a Chaos Emerald--runs away from home, Big trails him to Station Square. The goal of his stages is to [[FishingMinigame fish Froggy out of a body of water]].
21* '''E-102 "γ" (Gamma):''' One of Eggman's [[UnwillingRoboticisation animal-powered robotic enforcers]] who, after a chance encounter with Amy, gradually gains self-awareness and turns against his creator. His levels are {{timed mission}}s with ShootEmUp mechanics, with the player being encouraged to destroy chains of enemies to gain additional time.
22----
23''Sonic Adventure'' also has a VirtualPet side mode featuring a clan of {{mon}}s called the Chao, based on the A-Life system Sonic Team developed for ''VideoGame/NightsIntoDreams''. Chao can change their appearance and develop their attributes when given small animals collected from defeated robots in the main mode. These stats are put to the test in Chao Races, which pit your Chao against seven others in a race to the finish. This mode exists mostly outside the chronology and story of the main game, though winning the races is required for OneHundredPercentCompletion.
24
25The game saw an UpdatedReRelease for Platform/NintendoGameCube and PC in 2003, dubbed ''Sonic Adventure DX: Director's Cut''. It added special missions and some unlockable games from the Platform/GameGear library. It later became available for purchase on [[Platform/XboxLive Xbox Live Arcade]] and Platform/PlaystationNetwork, with the ''DX: Director's Cut'' extras [[DownloadableContent sold separately]]. A similar version popped up on Platform/{{Steam}} roughly six months later and with the ''DX'' version's extra content included. The post-2003 ports are missing the Game Gear spinoffs, unfortunately.
26
27A direct sequel, ''VideoGame/SonicAdventure2'', was released in 2001 to commemorate the series' [[MilestoneCelebration 10th anniversary]].
28
29----
30!!You know nothing, FOOL! IT'S TV TROPES, THE WIKI OF DESTRUCTION!
31[[foldercontrol]]
32
33[[folder:#-G]]
34* EleventhHourSuperpower: This is the first game to have Super Sonic treated as this, rather than as an added bonus for collecting all the Chaos Emeralds.
35* FifteenPuzzle: Plugging a controller with a VMU into controller port C or D into the Dreamcast while the game is on lets you play a minigame called ''Chao Puzzle'' that has 15 Chao-themed 3x3 slider puzzles to solve.
36* AbsurdlySpaciousSewer: Averted with Station Square's sewers, which are a realistic size, but played straight with those of Casinopolis. You get dumped in there if you lose a game of pinball and come away with less than 100 rings or you play the level as Tails.
37* AbusiveParent: Pachacamac didn't have any qualms about ordering his echidna soldiers to trample his own daughter just to get to the Emerald shrine.
38* ActionHoggingOpening: The FMV intro looks ''far'' more epic and impressive than most of the story depicted in-game.
39* AdaptationInducedPlotHole: Speed Highway's downtown section is connected to the town hall in Station Square's adventure field. It is also seen in ruins during the final boss fight. Problem is, ''DX'' messed this up by redesigning the building's look on the adventure field.
40* AIIsACrapshoot: Inverted with Gamma. Being one of Dr. Robotnik's creations, his AI was evil by design, but later malfunctioned and turned good.
41* AirborneAircraftCarrier: The Egg Carrier [[spoiler:and the Egg Carrier 2]].
42* AirVentPassageway: The game actually makes use of this trope a number of times in order to progress from level to level.
43** Sonic and Tails travel through the sewers of Casinopolis in order to find the Chaos Emerald located there.
44** This is also how Gamma and Amy choose to travel through the Hot Shelter in the Egg Carrier.
45* AllForNothing: At the end of Tails' story, Eggman, having lost both Chaos and the Egg Carrier, decides to destroy Station Square by blowing it up with a missile. But to his dismay, it fails to explode. He goes to detonate the warhead, but Tails beats him and disables it. Sadly, [[spoiler:in Super Sonic's story, Chaos has obtained the seven Chaos Emeralds and transformed into Perfect Chaos]], causing Station Square to be completely inundated and destroyed anyway. That said, the people of the city are still grateful to Tails for his actions, as seen in ''Sonic Adventure 2''.
46* AllThereInTheManual:
47** According to an official Sonic website, ZERO is the "zeroth" E-Series robot with the official designation of E-100 Alpha.
48** Said website also reveals that Chaos is a mutant Chao.
49** One of the game's official strategy guides gives names and E-Series numbers to all of the game's Badniks. Said guide also explains a little more of the ancient echidna tribe's backstory, such as Pachacamac's warmongering being pivoted by the death of his mother (Tikal's grandmother).
50* AllIsWellThatEndsWell: At the end of the game, [[spoiler:as the characters are recuperating after their battle against Perfect Chaos]], Tails invokes this trope verbatim in the English dub, despite the fact that the city has been completely inundated and destroyed.
51* AlmostOutOfOxygen: A staple of the franchise. That countdown music is unnerving.
52* AlreadyDoneForYou:
53** Given that the storylines (apart from the Super Sonic storyline) are done in a RashomonStyle, expect this to happen very often. For example, Sonic can only enter Speed Highway by getting the employee key card to unlock the elevator. When Tails goes to Speed Highway in his own story, the elevator is already unlocked.
54** However, it is just as often averted, somewhat confusingly. All characters present during a boss encounter fight the same boss in their story, even if another character already beat it in their story -- the most infamous example being Chaos 4, who must be fought by Sonic, Tails, ''and'' Knuckles.
55* AmusementPark: Twinkle Park, which serves as Sonic's fifth action stage and Amy and Big's first. Sonic's section starts out with him driving a bumper car through a race course, then search for the end-of-level capsule at the top of Pleasure Castle, which includes a roller coaster, a bowling minigame, and obstacles with an amusement park backdrop. Amy's section has her go inside Pleasure Castle, where she must evade ZERO through the hall of mirrors, while Big's section has him fish for Froggy in the pool near Pleasure Castle.
56* AnachronicOrder:
57** Because of the RashomonStyle nature of the story, the sequences where the characters see Tikal in the past are not played in order so it's up to the player to piece together what went down between Tikal and the Chao, her father and his tribesmen, and what prompted Chaos's vengeance. [[https://www.youtube.com/watch?v=2K30xVEdmXM This video]] attempts to show the sequence of events that led up to Chaos being unleashed.
58** In a {{downplayed|trope}} variant, the characters' actual stories don't begin or end at the same time. However, this is only visible if you pay attention to the NPC subplots. The most obvious tell is the lady who has a crush on a burger shop employee, but is [[ShrinkingViolet too shy to tell him]]; how far away she is from the burger shop indicates how far into the story you are. Through this, it's apparent that Sonic and Tails' stories start earlier than the other characters, while Amy's story ends last, as it's the only one where the burger shop subplot is resolved (the lady gets a job working at the burger shop).
59* AndTheAdventureContinues: Invoked by Sonic during the PreviouslyOn segment at the start of the Last Story; apparently he's in the habit of heading off on new journeys once the bad guys are beaten. For everyone else, this is an example of ButNowIMustGo.
60* AndThenWhat: When Tikal declares that [[spoiler:Perfect Chaos must be resealed within the Master Emerald]], Sonic asks her this. He points out that [[spoiler:Chaos will still be a ball of rage trapped by his own emotions, with the unspoken point that if he were freed again, he'd just go on another rampage]]. Tikal replies that they don't have any other options, until the other heroes provide one by bringing in the discarded Chaos Emeralds.
61* AndYourRewardIsClothes: In ''DX'', getting all medals unlocks Metal Sonic, who is essentially a reskinned Sonic with slightly altered animations. You can only use him in Trial mode.
62* AnimatedAdaptation: The whole game was adapted into an arc in TheAnimeOfTheGame ''Anime/SonicX'', as was its [[VideoGame/SonicAdventure2 sequel]].
63* AnotherSideAnotherStory: Play through the main story from 6 different perspectives. Each character also gets a piece of the backstory of Chaos and the echidna race, only by playing through all stories do you get the complete sequence. And, at least in the English dub, each story's dialogue subtly differs RashomonStyle to reflect the viewpoint of the player character.
64* AntiFrustrationFeatures:
65** The spirit of Tikal is often in the overworlds, giving you hints on where to go next if you touch it.
66** At certain points in Adventure Mode, the loudspeaker will announce "There are no trains in service at this time", which helpfully prevents wasting time running to the train.
67** In Sonic's Icecap, the timer stops until the player finishes the short cutscene in which Sonic gets on the snowboard, so that the player's time score doesn't get affected by it.
68** In Mission Mode, all of the missions are color-coded on the mission screen to indicate which characters have access to them.
69* ApocalypseHow: The destruction of the echidna civilization 3,000 years ago is a Class 1. Then [[spoiler:Chaos' destruction of Station Square]] is a Class 0.
70* AppropriatedAppellation: Sonic greets his arch-nemesis as "Eggman", who protests that his name is Dr. Robotnik. Later on, the doctor makes "EGGMAN" the password to the Chao Garden on the Egg Carrier -- he even boasts in the English version of ''VideoGame/SonicFrontiers'' that he took Sonic's insult and made it a name to be feared. This isn't present in the Japanese versions, where Eggman has always been the doctor's name -- instead, Sonic makes a simple remark that it's been a while since they've seen each other.
71* ArbitrarilySerializedSimultaneousAdventures: The game has six playable characters whose individual stories have to be completed before unlocking the final story that connects all six.
72* ArmedWithCanon: The localization team pokes fun at the "Robotnik" name debate just before the Egg Hornet battle. Dr. Robotnik throws a tantrum and insists on being addressed by his real name; everyone just ignores him and continues calling him Eggman.
73* ArtEvolution:
74** This game introduced the "modern" art style for Sonic and his friends that would be used in future games. Amy was the one affected most by this, as she no longer looks like [[DistaffCounterpart a pink Sonic in drag]]. However, the Sonic-themed pinball table in Sonic's version of Casinopolis ''does'' feature stock artwork from the earlier games.
75** Angel Island is noticeably redesigned from its Classic Era counterpart in ''[[VideoGame/Sonic3AndKnuckles Sonic 3 & Knuckles]]''. Here is [[http://info.sonicretro.org/images/6/6d/AngelIsland.png the original]], contrasted to [[https://i.imgur.com/Vsr1UIW.png this game's counterpart.]]
76* ArtificialStupidity:
77** Tails' levels have you race against Sonic, who is technically another player controlled by an AI. Because of this, Sonic tends to struggle when dealing with obstacles (which is particularly notable at the end of Casinopolis, where he takes a very long time just to jump through a bunch of spikes), but he makes up for this by [[TheComputerIsACheatingBastard rubber-banding his way to the goal]]. The last race against Eggman averts this because he's not an AI at all, instead he just follows a straight path to the goal.
78** The fights against the other playable characters in the game (such as Sonic vs. Knuckles) aren't much better, as they simply charge at you and don't bother dodging your attacks. Because of this, each fight will usually last under twenty seconds.
79* AscendedExtra: Amy, originally a semi-recurring side character beforehand, gained a prominent playable role in this and many titles following it.
80* AutobotsRockOut: The first example of the series. Sonic, upon harnessing the remaining positive energy within the Chaos Emeralds, transforms into Super Sonic and the main riff of "Open Your Heart" sets the scene. The theme also continues into the battle proper, providing the music for the first half of the fight.
81* AutomaticNewGame: Starting a new game results in you automatically starting Sonic's story.
82* BackForTheFinale: Though Gamma is gone by the end of his story, [[spoiler:the pink Flicky that was powering him shows up to represent him during Super Sonic's story]].
83* {{Balloonacy}}: A single balloon is all Amy needs to float away from ZERO's grasp.
84* BattleAtopThePoles: A one-way example. During the fight against Chaos 0, after Sonic knocks his health down to below half, Chaos springs himself into the air, hops from lamppost to lamppost, and after stopping, attempts to jab Sonic with his ExtendableArms from the top of a lamppost.
85* BattleInTheRain: Sonic's first encounter with Chaos 0 takes place during a stormy night.
86* BigBad: Each character has an antagonist that is more prominent in their campaign than anyone else's, making them the BigBad of the respective story:
87** Dr. Eggman for Sonic and Tails, with both stories centering around trying to stop the doctor's latest scheme.
88** Chaos for Knuckles, due to the former smashing the Master Emerald and beginning the plot for the latter's story. To reinforce this, in addition to the battles against Chaos 4 and Chaos 6 shared by other characters, Knuckles alone has a unique BossBattle with Chaos 2.
89** Amy's story has ZERO, the robot that chases after her in an attempt to kidnap Birdie.
90** Gamma's story plays with this. At the beginning, Sonic is the BigBad due to Gamma being one of Dr. Eggman's creations fully loyal to him. [[spoiler: After the halfway point, Eggman himself takes up the role, although the doctor himself is never fought or encountered directly. Gamma instead focuses on taking out the remaining E-Series robots, with his final showdown being against his older "brother" Beta]].
91** Big's story does not have an antagonist at all, with the story instead focusing on Big just trying to find his friend Froggy. While Big does have a brief showdown with Chaos 6, it's nothing more than fishing out Froggy and leaving rather than an actual fight, and Big never learns what Chaos is or why he took Froggy in the first place.
92** [[spoiler: Super Sonic's story has Perfect Chaos, with Chaos himself turning on Eggman and cementing himself as the true BigBad of the game]].
93* BigFancyCastle: Pleasure Castle serves as the centerpiece of Twinkle Park. Sonic's section has him climb atop it to look for the end-of-level capsule, while Amy's section has her go inside it to evade ZERO in the hall of mirrors.
94* BiggerOnTheInside: The Hot Shelter and Sky Deck suggest that the Egg Carrier is this.
95* BigNo: Pachacamac yells "No!" after [[spoiler:his conquest invites the wrath of a furious Emerald-powered Chaos onto his tribe]].
96* BittersweetEnding:
97** In Knuckles' story, he has finally recovered all of the pieces of the Master Emerald and successfully reassembled it. However, he's still bound to his mission to guard the emerald alone. He concludes that, while he's unsure why he was given this duty, he will continue to do it anyway.
98** In Gamma's story, Gamma dies after destroying his brothers to free the Flickies, but a Flicky of his own is free as well, setting up the ending in Amy's story.
99** In the final story, [[spoiler:Chaos is neutralized]], but Station Square is a flooded mess. It's rebuilt in the ''Anime/SonicX'' adaptation, while in ''Sonic Chronicles'', it's nothing more than a tumble-down shanty town in which the survivors live, located in Blue Ridge Zone.
100* BlackoutBasement: One section of Lost World is dimly-lit and requires Sonic to shine lights onto nearby mirrors to illuminate each part of the path. In the Dreamcast release, it's utterly pitch black unless you do, whereas in the DX version, there's just enough lighting that you can make your way through it without needing to bother.
101* BlindIdiotTranslation: Some of the mission descriptions in ''DX'' are translated clunkily to the point of being almost incomprehensible, with lines like "I hate this dark and filthy place! Can you find it?" and "A fugitive have escaped from the jail of burning hell! Find the fugitive!" standing out.
102* BlobMonster: Chaos, who's made of water.
103* BodyHorror: The way the scene of Gamma finding Beta being rebuilt following the training exercise at the beginning of Gamma's story plays out. Gamma's reaction is flatly neutral due to his monotone voice and lack of a face but the experience itself is designed to evoke a sense of Beta undergoing an unwanted transformation from the point of view of the player.
104* BondVillainStupidity: Early in both Sonic and Tails' stories, following Casinopolis, Eggman successfully ambushes them, hits them with KnockoutGas, and steals their recently-acquired Chaos Emerald. Rather than killing them immediately afterwards, or simply using a lethal gas to begin with, he just leaves them alone to wake up unharmed the next morning.
105* {{Bookends}}:
106** Knuckles' story begins and ends with him narrating how he was fated to stay forever on Angel Island guarding the Master Emerald. In the beginning, he mentions that he doesn't know why he was given this role in life, but in the end, he suggests he may be better off not knowing.
107** The game begins and ends with Sonic fighting Chaos. The first time, he fights Chaos 0. [[spoiler:In the last story, he fights Perfect Chaos.]]
108* BornAgainImmortality: The Chao can come back from death this way if raised correctly. In fact, dying and being reborn twice is one of the requirements for a Chao to become a perfectly immortal Chaos Chao.
109* BossArenaIdiocy:
110** The arena Amy fights [=ZERO=] in is enclosed by an electric fence. If you knock [=ZERO=] into the fence, it will reveal a button in its head. Hitting this button damages and ultimately self destructs it.
111** Knuckles would not have defeated Chaos 6 if it weren't for the ice robots scattered all over the arena (for Sonic's fight with Chaos 6, see TacticalSuicideBoss below).
112* BossArenaUrgency: After the Egg Viper takes five hits, Eggman will start to destroy the platforms you're standing on. If you don't finish him quick, you'll have nothing left to stand on and plummet to your death.
113* BossRush: Beating a story unlocks a mini-game where you fight each of the bosses faced in that story one after the other (the exception being Super Sonic, whose story ''only'' consists of a single boss fight with some Adventure Field navigation beforehand). Gamma's version is strangely restricted to only the Adventure Field battles against E-101 Beta [[spoiler:and E-101 Mark II]], lacking any of his in-level bosses.
114* BossOnlyLevel:
115** Outside of the three E-Series robots not named 101 in Gamma's story, all the boss fights and character duels are self-contained on the main adventure fields (though the last boss fights for Sonic and Tails start right after the player completes their final action stages, but are not directly connected to those stages outside of terrain).
116** The final storyline consists of a single boss fight, [[spoiler:Perfect Chaos]], strung together by cutscenes and some minor Adventure Field gameplay. Infamously, grabbing the Crystal Ring powerup in this story is a GameBreakingBug if you quit and reload without beating an Action Stage first, since the game doesn't know where to load from otherwise.
117* BossSubtitles: In the style of a typewriter.
118* BossTease:
119** Amy Rose's story and gameplay consists of being hunted by, and running away from, E-100 ZERO, a robot specifically designed to end your run and capture the small bird you're carrying. While you can temporarily slow it down in action stages, you can only really defeat it in your final encounter. Justified in that Amy can't access the tough robot's weakpoint without the electrified fences in the boss arena.
120** E-102 Gamma's story will, at one point, lead you into a cutscene wherein your "big brother", E-101 Beta, is being rebuilt in a funky new form, in what probably registers as robotic BodyHorror for poor Gamma and Beta. E-101 Beta Mk.II is the last boss for Gamma, to be fought much later.
121--->'''Gamma:''' "[[{{Understatement}} ...This is the wrong room.]]"
122* {{Bowdlerize}}: In the international versions, there is a rather innocuous billboard in Casinopolis. In the original Japanese version, this billboard was of a scantily-clad cowgirl with a fully-modeled martini glass... that moaned suggestively when jumped or glided into. The change was backported into the Japanese release with ''Sonic Adventure International'', and retained for all versions of ''DX''.
123* BrokenBridge: Parts of the Mystic Ruins, including Angel Island itself, are blocked off by pedestals that require [[PlotCoupon magic stones]]. The same goes for Station Square, except that the keys are more mundane. Also, after the Tornado crashes, Sonic (who landed in Station Square) and Tails (who landed in the Mystic Ruins) can't reunite because the train isn't running since the workers have gone on strike, with striking workers standing outside the station in Station Square (all of the characters except Big get to deal with the strike blocking access to or from Station Square). And lastly, if the player exits Tails' last Action Stage before completing it[[note]]you enter Tails' Speed Highway and the race against Eggman automatically after defeating Gamma on the Egg Carrier[[/note]], the trains will not be operating because there is a missile crisis going on and the train operators are helping people evacuate.
124* BrokenRecord: Get used to hearing Eggman say "Get a load of this!" a lot during final battles against the Egg Viper and the Egg Walker at the end of Sonic and Tails' respective storylines.
125* ButNowIMustGo:
126** According to the PreviouslyOn segment at the start of the Last Story, Sonic was planning to head out on his next journey after his nap, since Eggman appeared to have been defeated. His plans were interrupted once Tikal found him.
127** After the defeat of the TrueFinalBoss, [[spoiler:both Tikal and Chaos AscendToAHigherPlaneOfExistence at the end of the story, while Sonic goes running off]]. Notably, Station Square is still in ruins when this happens.
128* ButThouMust: Despite Big being able to walk straight to Sonic's plane, which he uses to escape the Egg Carrier, [[StupidityIsTheOnlyOption he has to detour to the boss arena for Chaos 6 before he decides to do so.]]
129* CallBack:
130** Icecap first appeared as "[=IceCap=] Zone" in ''Sonic the Hedgehog 3'', and it featured a snowboarding segment, too. Red Mountain's inner section is also clearly part of Lava Reef from ''Sonic & Knuckles''. Both are set on Angel Island.
131** After the Sky Chase minigame, Tails has a {{flashback}} to his first meeting with Sonic, originally narrated in the Japanese ''VideoGame/SonicTheHedgehog2'' manual.
132** Amy Rose has a {{flashback}} to her kidnapping in ''VideoGame/SonicTheHedgehogCD''.
133** The ending to Sonic's story mode is more or less a 3D tribute to the ending of ''VideoGame/SonicTheHedgehog1'', complete with Sonic's YeahShot into the camera.
134** The cutscene right after the player beats Red Mountain during Sonic's story seems to be a call-back to the cutscene before the final level in ''Sonic the Hedgehog 2''.
135* TheCameo:
136** [=NiGHTS=], from ''VideoGame/NightsIntoDreams'', has their own pinball board in Casinopolis and will even appear in person sometimes.
137** [[VideoGame/SonicTheHedgehogCD Metal Sonic]] and [[VideoGame/SonicTheHedgehog2 Mecha Sonic]] appear in stasis tubes at Eggman's Mystic Ruins base.
138** [[VideoGame/SonicR Tails Doll]], along with doll versions of Knuckles and Sonic, appear as training dummies in Gamma's first level and Sonic's tenth and final level.
139** In the ''DX'' version, Cream the Rabbit appears at certain points in the Adventure Field (only in Station Square), and Chris Thorndyke from ''Anime/SonicX'' appears as a billboard in certain missions.
140* CannotSpitItOut: A ShrinkingViolet in Station Square has a major crush on the guy who works the counter at the Burger Shop. She can't muster up the courage to tell him how she feels, so, she ends up hanging around the shop all day, not saying anything. From his vantage point, she's a StalkerWithACrush. Towards the end of the entire game's storyline, she figures out a way to overcome her problem: get a job at the Burger Shop alongside her object of affection.
141* CaptainObvious:
142** Quite a few snarky moments if you look closely.
143--->''[the Egg Carrier changes its shape]''\
144'''Tails:''' Ahhh, wow! It's changed shape. Did you see that?\
145''[Sonic gives him a weary look, and ignores him]''\
146'''Sonic:''' Darn! This makes it harder for us to get to the bridge! \
147'''Tails:''' [[LampshadeHanging I hate it when he doesn't listen...]]
148** Also, Gamma, due to being a robot. He states:
149---> '''Gamma:''' ''[when transported into the past via a vision]'' This presents a problem.\
150'''Gamma:''' ''[after seeing what happened to Beta after defeating him at the beginning]'' This is the wrong room.
151* CasinoPark: Casinopolis, which serves as Sonic's third action stage and Tails and Knuckles' second. In Sonic's section, Sonic has to play the games to earn at least 400 rings to deposit into the safe to get the White Chaos Emerald at the top. Losing a pinball game with less than 100 rings will send him into the sewers, where he must find his way out, which forms the entirety of Tails' section. Knuckles' section has him search for the pieces of the Master Emerald in the lobby.
152* CerebusSyndrome: The game has a darker, more shonen-anime esque tone than its predecessors. The real antagonist, Chaos, isn't a standard "take over the world" bad guy, but a vengeful, mourning creature of god-like power who wiped out an entire civilization (and this is also the first game in the series where characters are explicitly killed, albeit off-screen) and is stated to have come ''very'' close to causing an apocalyptic scenario. The stakes are raised much higher here than in any of the previous entries.
153* ChaosArchitecture: Angel Island got a substantial redesign, and in particular a new outdoor shrine for the Master Emerald that served as a point of connection with the ancient echidna society of the past.
154* CharacterDevelopment:
155** Tails learns to take on troubles without Sonic's help, and he even musters up the courage to stop Eggman's attack on Station Square.
156** Knuckles, who starts the story wondering why he was tasked with guarding the Master Emerald, accepts his duty after learning more about his echidna ancestors.
157** Amy goes from being a DamselInDistress depending on Sonic to save her to an ActionGirl beating up the very robot that constantly pursued her.
158** Gamma learns about love and caring, which motivates him to stop being a mindless servant to Eggman, go on his own mission, and eventually has to die to free the bird trapped inside of him.
159* CharacterizationMarchesOn: This game marks the first time Knuckles is portrayed as stoic and serious in contrast to his debut in ''[[VideoGame/Sonic3AndKnuckles Sonic 3 & Knuckles]]'' where he was constantly laughing at you when he activated one of his traps.
160-->'''Unknown From M.E.:''' Unlike Sonic, I don't chuckle. I'd rather flex my muscles!
161* ChekhovsGun: The Chaos Emerald inside the Tornado 2. It plays a major role in setting off the events for the Super Sonic chapter.
162* ChekhovsGunman: Retroactively. Metal Sonic appears in Amy's story in a flashback of ''Videogame/SonicCD'', and as a EasterEgg inside Eggman's base in Mystic Ruins. He would return as the BigBad in ''Videogame/SonicHeroes''.
163* ChildProdigy: Tails was implied to have this in previous games, but this is probably the first major series game [[note]]''VideoGame/TailsAdventure'' and ''VideoGame/SonicTheFighters'', minor spinoff games, notwithstanding[[/note]]which shows the full extent of his technical skills, such as his mechanically powered house and his transforming airplane.
164* ClimaxBoss: Several for different character modes, mostly aligned to their CharacterDevelopment:
165** The Egg Walker is the FinalBoss of Tails' story, culminating in him developing independence from Sonic and stopping Eggman on his own.
166** The Sonic/Tails vs. Gamma boss. While pathetically easy whoever you play as, it occurs just after Gamma's PetTheDog moment releasing Amy from an unknowing Eggman, leading Amy to break up the fight and provoke his HeelFaceTurn.
167** Also E-101 Beta Mk II, Gamma's FinalBoss, happening straight after Gamma establishes its ForegoneConclusion that it will sacrifice itself to complete its E-Series rescue mission.
168* ColorCodedCharacters: As shown on the character select screen, each character's menu items are shown in a different color:
169** Sonic - Blue
170** Tails - Orange
171** Knuckles - Red
172** Amy - Pink
173** Big - Purple
174** Gamma - Gray
175** Super Sonic - Yellow
176* ComicBookAdaptation: Was adapted in story arcs in ''ComicBook/SonicTheHedgehogArchieComics'' and also as what was notably the last new story arc in ''ComicBook/SonicTheComic''.
177* TheComputerIsACheatingBastard:
178** Present in Tails' stages, specifically of the RubberBandAI variety.
179** More infamous is [[InconsistentSpelling Chaclon/Chacron]], a Chao that shows up in the Chao Races upon their completion. What makes him a cheater is that he's constantly in the "boost" state and runs right past the tree he's supposed to shake. He graciously gives the competition a head start, but once that time is up, he'll burst right out of the gate.
180* ConflictBall:
181** Knuckles' fight with Sonic relies heavily on ContrivedCoincidence and PoorCommunicationKills, what with Knuckles immediately attacking and demanding the Master Emerald shards after catching a mere glimpse of the green Chaos Emerald that Sonic is actually holding.
182** In E-102's story, Eggman keeps putting E-102 in competition with his brothers to see who's the "best"--first with E-101 Beta at the start of his story and then with E-103, E-104, and E-105 in the competition to find Froggy--for no apparent reason. It doesn't help that he punishes the losers with {{Painful Transformation}}s that make them more lethal and occasionally monstrous.
183* ConsoleCameo: E105ζ (E-105 Zeta) is made of six Dreamcasts [[http://info.sonicretro.org/File:E105.png located around the grey blocks under his cannons.]]
184* ContinuityNod:
185** There's this line:
186--->'''Sonic (to Knuckles):''' [[VideoGame/Sonic3AndKnuckles Did Eggman trick you]] ''[[VideoGame/Sonic3AndKnuckles again]]''?
187** One of Amy's memories is of Sonic saving her in ''VideoGame/SonicTheHedgehogCD''. However, [[SuddenlyBlonde the models weren't changed]].
188** When playing other characters' stories, your allies will sport any power-up accessories you picked up for them in their stories (although this can also create a ContinuitySnarl since you'll see characters with upgrades at points before they received them in their own stories, such as Sonic wearing the Light Speed Shoes when he comes to rescue Tails in Emerald Coast).
189** After getting their powers drained [[spoiler:by Perfect Chaos]], the Chaos Emeralds look the same as the Super Emeralds did in ''[[VideoGame/Sonic3AndKnuckles Sonic 3 & Knuckles]]'' in their powerless state (except for the size, of course), prior to being fully restored by the player.
190** Tails has a dream reminiscing his first meeting with Sonic, as previously told in the Japanese manual of ''VideoGame/SonicTheHedgehog2''.
191** In the Japanese version, a random NPC makes reference to Sonic's prior adventures in [[VideoGame/SonicTheHedgehogCD Little Planet]] and [[VideoGame/Sonic3AndKnuckles Angel Island]].
192** Amy wields the Piko Piko Hammer, which she was first seen with in ''VideoGame/SonicTheFighters''. As a nod to this, one of its upgrades is called the Warrior Feather ("Fighters Feather", in the original Japanese release).
193** Another thing that would have been lost to most non-Japanese players is that the game's story makes major references to a number of lore details mentioned in [[AllInTheManual the classic games' Japanese manuals.]] For instance, the background with an ancient prosperous civilization attempting to misuse the Chaos Emeralds before being wiped out overnight for their actions was first narrated in the Japanese manuals of ''[[VideoGame/SonicTheHedgehog2 Sonic 2]]'' and ''[[VideoGame/Sonic3AndKnuckles Sonic 3]]''. Similarly, Chaos and his [[OneWingedAngel dragon-shaped ultimate form]] are a reference to the story prologue from the Japanese ''Sonic 3'' manual, which mentions an ancient mural predicting the forthcoming of a legendary dragon that would bring disaster after coming out of an egg.[[note]]The "egg" in this case is likely the Master Emerald, although it could alternatively be referencing the fact that Chaos was born out of an egg, going by the fact he's actually a mutated Chao[[/note]] [[https://info.sonicretro.org/images/2/2d/SA1_PerfChaosMural.PNG A similar mural]] is seen in Lost World.
194* ContrivedCoincidence: Eggman lies to Knuckles that Sonic is collecting the pieces of the Master Emerald, but what really causes Knuckles to seize the ConflictBall is seeing Sonic at an angle that just so happens to partially expose the green Chaos Emerald to Knuckles' eyes.
195* ConvectionSchmonvection: Sonic and Gamma can survive just fine in the incredibly hot volcano section of Red Mountain, with lava and geysers being the only hazards that damage them. Then again, this is true of all ''Sonic'' games where the characters don't suffer any ill effects from standing only a few inches above a lava pit.
196* CrazyPrepared: Eggman. Not only does he have the God of Destruction at his command, he has a giant flying carrier (although it functions more like a battleship), [[spoiler:a second carrier to use against Chaos if it goes rogue, a ''huge'' missile stationed off the coast of Station Square should the Egg Carrier and Chaos be defeated]], and a giant base in the middle of Mystic Ruins. All of this raises the question, however, of why he needs to gamble with controlling the God of Destruction to destroy just one city with all of these fairly potent back-up plans.
197* CreatureBreedingMechanic: Both games include Chao gardens. Chao may be trained and any two may be crossed, with the usual [[LamarckWasRight Lamarckian]] mechanics coming into play. This doesn't affect anything outside of the garden, though.
198* CriticalExistenceFailure: As in most games in the franchise, Sonic and the cast can take any amount of damage, from a barrage of Eggman's launched missiles to an explosion a third the size of the Egg Carrier, without any outward sign of injury, but after their last ring is lost, brushing against a robot chimp is enough for a K.O.
199* CrystalPrison: The Master Emerald is this to Chaos.
200* CueTheSun: The end of Speed Highway. Its BGM is appropriately called "At Dawn."
201* CurbStompBattle:
202** In the final route of the game, [[spoiler:Eggman hops into the Egg Carrier 2 to tame Perfect Chaos. It's on-screen for maybe ten seconds before Perfect Chaos blows it up]].
203** The Sonic/Tails vs. Gamma battles usually play the outcome as such, depending on which character is playing. In Amy's case, Sonic is winning, but with Gamma still holding ground.
204* CutsceneIncompetence: ''Many'' cutscenes, due to the generally stilted choreography. Sonic in particular seems to forget how to run and ends up walking to close distance when he ''needs'' to run to prevent something bad from happening.
205* CutscenePowerToTheMax:
206** Now we know why Sonic refuses to sit in the cockpit of Tails' plane -- because gravity means '''nothing''' to him. He survives falling several kilometers to the ground not once, but ''twice'' in the game. The second time, Sonic's body endures a comical pancake effect when he hits the ground, but he's no worse for wear.
207** In Tails' ending, he manages to fly all the way from Station Square to the Mystic Ruins without getting tired.
208* DarkerAndEdgier:
209** Especially compared to most ''Sonic'' games released before it. It's nothing compared to, say, ''VideoGame/SonicAdventure2'' or ''VideoGame/ShadowTheHedgehog'', but this game literally starts off with an opening FMV depicting a city being flooded, and later in the game, we see [[spoiler:the echidna tribe kill the Chao, before being wiped out themselves]].
210** Gamma's story is this to the rest of the game, complete with an explicitly BittersweetEnding. Super Sonic's story has a somewhat grimmer tone than the rest of the game as well, in which the destruction of Station Square foreshadowed by the aforementioned cutscene takes place.
211** Eggman also plays a more NoNonsenseNemesis role in this, relying on cunning to collect the Chaos Emeralds and generally not putting on more of a show than necessary. By the end of Tails' story, he's also very agitated and ready to kill anyone who gets in his way without mincing words (this carries over into the end of Sonic's story, which takes place afterwards, where he's in no mood to put up with Sonic's 'tude).
212* ADayInTheLimelight: Tails, Knuckles, and Amy, who are generally supporting characters in Sonic's adventures, all have their own campaigns here that greatly flesh out their characters. Particularly noticeable with Amy since she was mostly relegated to cameos in spin-off titles prior to this game. This game also marks the first time you play a character from Eggman's perspective, as Gamma starts off as a part of his crew before defecting.
213* DeadlyRotaryFan: Spinner and Thunder Spinner are fitted with these. Speed Highway also features a HelicopterBlender obstacle.
214* DeconstructedTrope: E-102 Gamma's storyline is an unexpected deconstruction of Eggman's robotic {{mook}}s... or more specifically, the fact that [[UnwillingRoboticisation Eggman's robots are powered by animals]]. (Well, technically, Gamma was an EliteMook, but whatever.) After seeing Amy's flicky in the Egg Carrier's prison chamber, his power source's memories and emotions began to conflict with his programming, eventually leading to his seeking out and destroying the other E-100 models (and himself) to free the animals inside.
215* DenserAndWackier: Big's story is much more offbeat and lighthearted compared to most of the other character modes.
216* DepartmentOfRedundancyDepartment: The stage tracks for both Adventure games have a naming convention where they list the track name "...for [Stage Name]". This leads to redundancies such as "Run Through the Speed Highway ...for Speed Highway" or "Sky Deck A Go! Go! ...for Sky Deck."
217* DevelopersForesight:
218** If you're thinking bringing a bunch of rings into Casinopolis from the adventure field (probably for an instant emblem), don't bother. The game will just reset your ring count to zero.
219*** In the same vein, it is impossible to grind rings in Casinopolis to use them in the Chao Garden's Black Market in ''DX'', as rings from this stage (and only this stage) do not get added to the total count.
220** In general, this game averts WelcomeToCorneria. Every major story event leads to new dialogue from the [=NPCs=], who usually comment on recent story developments. Head back to Station Square as Amy between escaping the Egg Carrier and going to Final Egg, and there will be fewer [=NPCs=], with a good deal of the remaining ones talking about the missile that Eggman launched at the city. [[TheApocalypseBringsOutTheBestInPeople The train strike has even stopped to help with evacuation.]]
221** Big's adventure stages have distinctly little to do with speed relative to those of the other playable characters, so they aren't timed and he doesn't have the traditional checkpoint goalposts. Instead, the weight of the largest fish Big catches is recorded and retained in the event that Big dies or his fishing line breaks.
222** Even though there is little opportunity to drown in this game, and the odds of it happening are long to match, the production team went ahead and included drowning animations and vocal effects for all of the playable characters except for Gamma, in addition to bringing the classic drowning music up to full orchestral caliber.
223*** Gamma can't go into water, because he'd short out and break if he did. Instead, he compresses his body and deploys a propeller so he can hover over water. [[AwesomeButImpractical It makes caring for Chao more difficult]].
224** There are points in each character's story where they are locked into a specific adventure field for plot reasons, and cannot leave to go to another. Savvy players may think to go to the Chao garden, which has teleporter pads leading to the other adventure fields. However, doing so during these points will reveal the teleporter pads have been disabled, preventing the player from doing exactly that.
225* DeviousDolphins: Emerald Coast features a giant orca that tries to eat Sonic, destroying a bridge and a ramp in the process.
226* DigAttack: Knuckles can dig underground once he finds the shovel claws upgrade. This is mostly used to find Master Emerald pieces that are buried underground, starting with Red Mountain (the first Knuckles action stage played after Knuckles obtains the claws) [[note]]you find the claws in a cave that locks you in, and then you need to dig in a hole here to retrieve a "Monkey Destruction Switch" needed to blow up two Cage Kikis, the first to leave the cave, and the second who guards the entrance to Red Mountain[[/note]]. ''VideoGame/SonicBattle'' takes this one step further by having Knuckles' burrow ability as a special move, in which after he goes underground, he can move under an enemy and pop up from below to his or her surprise.
227* DidntThinkThisThrough: Tails modifies his plane so he and Sonic can fly up to the Egg Carrier. This seems to go smoothly until Tails realizes he forgot to equip landing gear ''just as they're about to land the plane''.
228* ADogNamedDog: Big isn't too creative with the names, as his frog friend is named Froggy.
229* DoingInTheWizard: In-game, Chaos is consistently portrayed as being some kind of genuine deity that the echidnas worshiped, and having some unexplained connection to the Chaos Emeralds and the Chao -- where exactly he came from is never explained in the story. Out of universe, Sonic Channel's profile of the character claims that he is just a Chao mutated by the energy of the Chaos Emeralds.
230* DoubleKnockout:
231** This happens after the Sonic (or Tails) vs. Knuckles fight, both characters run up to each other to attack, only to knock each other to the ground, followed with Sonic or Tails dropping the two Chaos Emeralds, which are then immediately taken by Eggman and fed to Chaos (this creates Chaos 4; the vs Knuckles fight on all sides goes directly to the Chaos 4 boss fight).
232** This can happen in the end of the Egg Viper boss battle, in which it specifically [[TakingYouWithMe tries to take Sonic down with it]].
233* DoWellButNotPerfect: Getting two emblems for completing some minigames, such as Twinkle Circuit, involves beating the top score twice. Having to beat your own score for the second emblem means that doing too well the first time will make things harder the second time around.
234* DownloadableContent:
235** Sega released a lot of this, which a player could download onto their [=VMUs=] (Visual Memory Unit). You could [[https://www.youtube.com/watch?v=LOxuMgwYwMs celebrate Christmas]] or [[https://www.youtube.com/watch?v=0s5zetlnnVM the year 2000]], in addition to [[https://www.youtube.com/watch?v=gXecwRD0l4Q the launch of the Dreamcast in the United States]], or [[https://www.youtube.com/watch?v=KrVsGtnpOXo try to win sportswear from Reebok]]. A GameMod for the 2004 PC version ported all the DLC and also provided translations for the non-English packs.
236*** Of note is the Japanese "Kadomatsu '99"[[note]]A Japanese decoration signifying the passing of a new year[[/note]] DLC, which was thought to have been lost due to no one preserving the save files. However [[https://www.youtube.com/watch?v=1-pCOMUVRzQ over twenty years later]] it was retrieved thanks to a random purchase of an old memory unit. It has since been integrated into the above-mentioned mod for the PC version.
237*** The maker of the PC mod also released his own [[https://dcmods.unreliable.network/index.php/2020/09/08/sonic-adventure-tikals-challenge-dlc-contest/ custom]] DLC pack. This can be played on a real Dreamcast or in the PC's DLC mod.
238** In the Xbox 360 and [=PlayStation=] 3 ports, the unlockable Metal Sonic and Mission Mode from ''DX'' needs to be bought separately. Averted with retail PC and later Steam versions which kept the ''DX'' version's content.
239* TheDragon: Chaos to Eggman. [[spoiler:[[DragonWithAnAgenda If just to get the Emeralds.]]]] Gamma's role in preserving him and helping against the heroes prior to a HeelFaceTurn may apply them as CoDragons.
240* DragonWithAnAgenda: Chaos only helps Eggman to get the Emeralds so that [[spoiler:Chaos can go OneWingedAngel and destroy the world]].
241* DramaticDrop: In the opening cutscene of Amy's story, she drops the bag of groceries she's holding upon seeing the Egg Carrier flying overhead.
242* DreamSequence: The visions of the echidnas' ancient history work as this.
243* DrearyHalfLiddedEyes: Some Chao that can have this as a default expression, but most notably Chacron. Players might think they're in for an easy race because of his sleepy look (even giving the other Chao a head start in the first game while he just lies down) before suddenly [[RubberbandAI jolting past absolutely everyone]].
244* DropTheWashtub: What happens if you input the wrong password while trying to get into the Egg Carrier Chao Garden.
245* DubInducedPlotHole:
246** The game's story expands on elements from the Japanese manuals of the Mega Drive games, including an ancient tribe guarding the Chaos Emeralds and a dragon fated to destroy the world. Due to other countries replacing the game plots with their own or simplifying them, the different direction and tone led to confusion from many western fans.
247** The English translation establishes that "Eggman" is a mocking nickname Sonic gave Dr. Robotnik, while he was always named "Dr. Eggman" in Japan. This raises the question of why he would make "EGGMAN" the password to the Egg Carrier Chao Garden.
248** If you go to the Angel Island section of Mystic Ruins as Sonic and stay still for a while, he'll say "So this is Angel Island", as if he had never been to the place before. In the Japanese original, his line was "Isn't this Angel Island?" instead, indicating that he was recognizing the place.
249** Most infamously, Tails declares "All is well that ends well" at the end, ignoring the fact [[spoiler:Perfect Chaos]] just destroyed the city. In the Japanese version, he just expressed relief that [[spoiler:Perfect Chaos]] had been stopped.
250** In the cutscene before the Egg Viper, Eggman sounds strangely casual and confident considering that the last time we saw him he [[VillainousBreakdown had snapped]] following the destruction of the Egg Carrier and defeat of Chaos 6, leading to him trying to nuke Station Square ''with himself in it'' -- and even ''that'' was foiled, [[UnderestimatingBadassery by Tails of all people]]. This was another weird dub change; the Japanese original had him acting more desperate and on the edge. This also explains his wild mannerisms in that scene.
251* DubNameChange:
252** Not unlike ''Super Mario 64'', this game marks the transition from a dub name to the original name and does so by using both, in this case Dr. Robotnik and Dr. Eggman.
253** Outside of the obvious turning point for the series villain, a few minor elements were renamed when the game went International, such as Mystic Ruin to Mystic Ruins and Spina to Spinner.
254** Two of the upgrades had their names changed — Rhythm Brooch became Rhythm Badge and Fighters Feather became Warrior Feather (though its Japanese name, "Senshi no Hane", is a more-or-less literal translation). All the others have the same (English) name in both versions of the game.
255* DubPersonalityChange:
256** Eggman and Sonic's first interaction changes between the original Japanese and the English translation. In the original Japanese, Eggman greets Sonic in an [[AffablyEvil amicable way]] as Sonic remains cautious. In the English dub, Sonic mocks Eggman by telling Tails "look, a giant walking egg", to which Eggman angrily responds "Silence! I am Doctor [[DubNameChange Robotnik]]!", seemingly to justify the name of Eggman in western territories.
257** The dub gives Sonic TotallyRadical dialogue and has him [[BigStupidDoodooHead address his opponents by insults and nicknames]], making him come off somewhat more hyper and childish. The original Japanese script had him use the occasional GratuitousEnglish instead, and gave him a more cool and composed demeanor, acting more nonchalantly in front of his enemies. In addition, some of the nuance and quirks of his original dialogue and demeanor were downplayed or LostInTranslation.
258* DuelingPlayerCharacters: The game has Sonic and Knuckles fight again, and he also duels with Gamma. However, playing through as Knuckles and Gamma allows the player to fight Sonic, and playing as Tails puts him in these fights instead of Sonic.
259* DullSurprise:
260** Due to the technical limitations of 3D modeling from back then, the cutscenes depict the characters with very blank or basic expressions and rigid to nonexistent body language -- many cutscenes just have the characters standing in idle, neutral poses while talking. It's somewhat jarring compared to the elaborately choreographed cutscenes seen in later games.
261** The English voice acting can also be like this, such as [[https://www.youtube.com/watch?v=demZZpIWMyA Knuckles' absolutely apathetic "oh no" whenever Sonic hits him during their fight.]] (It was clipped out of context from a ''beta'' cutscene, for some reason.) Gamma has this [[RoboSpeak completely intentionally]], though. Then there's the scene where Tails is about to crash his plane near Sonic at the beginning of Sonic's story, and [[https://youtu.be/yJg99CixMqU?t=17 Sonic reacts to it very dully.]]
262* EarlyInstallmentWeirdness:
263** ''Sonic Adventure'''s A-Life system differs significantly to all the other versions used from ''Videogame/SonicAdventure2'' onward. Neutral Chao were the only ones available in the game, and normal color baby Chao used the blue and green coloration of the Neutral/Normal evolutions instead of their usual blue and yellow, though the ones in the cutscenes had this. Coconuts grew at an insane rate compared to the ones in ''Sonic Adventure 2'' and even the ''DX'' version, feeding them increased a Chao's tiredness and boosted their max HP (a stat not present in any other game with Chao) and falling coconuts could hurt them. While throwing a Chao will only upset them, attacking them causes them to lose HP, and they will die their HP reaches zero -- even the immortal Chaos Chao -- in the original Dreamcast release. Chao sounded and behaved quite differently, and used animal trait actions much more often, while the changes that took place during second evolution happened to be absolutely insane and often broke their models.
264** While [[VideoGame/SonicAdventure2 future]] [[VideoGame/SonicTheHedgehog2006 games]] had multiple gameplay styles, they all, to some extent, had a heavy focus on platforming and action. This makes Big the Cat's fishing gameplay in ''Sonic Adventure'', which is required to make it to the Final Story, far stranger and more out of place in hindsight.
265** This is the only 3D ''Sonic'' platformer to lack a ranking system or grinding on rails, which were both introduced by [[Videogame/SonicAdventure2 its sequel]].
266** Sonic has to charge the Light Speed Dash (done by holding the Action Button) for several seconds to use it, while in future games, tapping the Action Button when touching a trail of rings is sufficient.
267* EarnYourHappyEnding: All six character stories, though it's rather bittersweet in Gamma's case.
268* EasterEgg:
269** Collecting rings as Sonic in Casinopolis will build up a golden statue of himself in the lobby. It takes 5,000 rings to fully complete it, even though only 400 are required to beat the level.
270** Cream the Rabbit [[ProductionThrowback makes a short appearance]] in ''DX'' when a player character exits Casinopolis. [[https://www.youtube.com/watch?v=wexxG6IaNi4&feature=related See video here.]]
271** This one should take a couple minutes to get to — a hidden [[https://www.youtube.com/watch?v=NBtkugzC6Uo room]].
272** Each character's story provides PreviouslyOn segments that cover the previous events in their story and indicate what they are currently doing. Some of these PreviouslyOn segments can only be found and read under very specific circumstances that require a certain amount of SequenceBreaking. Gamma has one segment, for example, that only appears if Amy is unlocked in Gamma's story when they meet each other in the prison (which almost never happens, since Amy is more often unlocked in Sonic's story).
273* EggshellClothing: In ''DX'', Chao can wear eggshells on their heads. It can only be removed if you toss the Chao at a wall. Both halves of an eggshell completely disappear in the original Dreamcast version when a Chao hatches.
274* EldritchAbomination: Chaos, a slime creature whose innards can be seen through it. They get more mechanical as he absorbs more Emeralds, until his final form.
275* EliteMook: The E-100 Series robots were designed by Eggman to be more more intelligent and dangerous than his normal Badniks. Gamma can challenge Sonic just on his own, and in his own story comes seconds from defeating him outright.
276* EmbeddedPrecursor: ''DX'' includes all of the Game Gear ''Sonic'' games available to unlock, by collecting enough Emblems.
277* EmotionalPowers: "The servers are the 7 Chaos. Chaos is power... ''Power enriched by the heart.'' The controller is the one that unifies the Chaos." This plays into the game's finale, where [[spoiler:a vengeful Perfect Chaos, empowered by the negative energy of the Chaos Emeralds, invokes flooding that could destroy the entire world, but the main characters use the Emeralds' remaining positive emotions gained along their respective journeys to empower Super Sonic and calm Chaos down through a final fight.]]
278* EternalEngine: Final Egg. Sky Deck and Hot Shelter to a lesser extent.
279* EtTuBrute: In Super Sonic's story, [[spoiler:Chaos has had enough of listening to Eggman, attacks him, and operates by himself in getting all the Chaos Emeralds to become Perfect Chaos.]]
280* EvilIsNotAToy: Eggman intends to use Chaos's power to destroy Station Square and build Robotnikland on its remains, but this turns on him when it's revealed [[spoiler:Chaos is the one using Eggman, so he can get the Chaos Emeralds and exact his revenge]].
281* ExpositionFairy: Tikal is always there to guide the player.
282* ExpositoryPronoun: In Japanese, Gamma initially refers to himself with the formal neutral pronoun "watashi", but near the end of his story, he switches to the informal and masculine "boku" when he realizes that he must self-terminate in order to complete his mission, indicating his gradual humanization.
283* {{Expy}}: Twinkle Park is one for Sega's Joypolis amusement park.
284* FailedASpotCheck: While it's not acknowledged by the characters themselves, Sonic is shocked to hear from Tails that Angel Island has fallen again during the Super Sonic story, despite the fact that he is lying down in view of where it fell.
285* {{Fanfare}}: While addressing his robots, Eggman plays his own [[https://www.youtube.com/watch?v=fg3ezY6aDV4 canned fanfare music]]. Pretty amusing.
286* FantasyKitchenSink: A superpowered deity, abandoned civilizations, fantasy magic, ghosts, time travel and talking animals are all present in the game, with some science fiction elements and even a [[WhatMeasureIsANonHuman "Ghost in the Machine" story]] for one of the major characters sandwiched in.
287* {{Filler}}:
288** Big the Cat's plot has almost no bearing on the rest of the game's storyline. The only thing that ties him into it is that his pet frog swallowed an Emerald, and has Chaos' tail.
289** Similarly, Amy's plot is only tied in via the Emerald her Birdie is holding (which is stolen halfway in) and her being the catalyst for Gamma's HeelFaceTurn, which ironically ends his own relevance to the central story.
290* FireForgedFriends: Implied with Big and Sonic. After retrieving Froggy on-board the Egg Carrier, Big muses to himself that they should escape before they're noticed, [[TemptingFate as he figures no one would bother to save either of them if they ended up in danger.]] Sure enough, Chaos winds up capturing Froggy shortly afterwards, though Sonic comes to both of their rescue. After the game concludes, Big becomes a semi-recurring friend of Sonic's.
291* FishingMinigame: The goal of each of Big the Cat's stages is to fish Froggy out of a body of water. The B-rank missions require him to catch a fish weighing at least 1000g and then Froggy, and the A-rank missions require him to catch a fish weighing at least 2000g and then Froggy.
292* FiveRoundsRapid: The cops unloading their magazines at Chaos 0.
293* FixedCamera: Made more adjustable in the ''DX'' version, and its later ports implemented analog camera controls.
294* FlawExploitation: Eggman, once again, tricks Knuckles into fighting Sonic as a way to nab two Chaos Emeralds. To a lesser degree, the first Emerald is nabbed from an opening when Sonic and Tails get cocky post-battle with Eggman's Egg Hornet.
295* FloatingContinent: Angel Island before the Master Emerald was shattered, and Windy Valley. [[spoiler:Angel Island only broke away from the mainland after Tikal used the Master Emerald to stop Chaos' rampage by sealing them both in it.]]
296* {{Foreshadowing}}:
297** The fact that Tikal had actually managed to send Gamma's mind to the past foreshadows him becoming sentient in his chapter.
298** At the start of Knuckles' story, when the Master Emerald is broken, you can see a Hint Ball (in other words, Tikal's spirit) fly out of it.
299** When Eggman introduces the Egg Carrier to Sonic, Tails, and Knuckles, he notes that it "pales in comparison to the power of Chaos". [[spoiler:When he pulls out a second Egg Carrier during the Last Story, Perfect Chaos swats it out of the sky in a matter of seconds.]]
300** In Final Egg, Sonic & Amy will occasionally face off against a badnik known as the Egg Keeper, which can float, speed forward, and can capture the player. This otherwise one-off enemy serves as a foreshadowing for both Gamma's final boss, which utilizes the same propulsion method, as well as an enemy from a later game, ''VideoGame/SonicHeroes'', which has a similar means of halting the player's progress.
301** After Gamma first defeats Beta and earns Robotnik's permission to serve aboard the Egg Carrier, Beta silently insists on coming along with them. Annoyed, Robotnik rolls with it and allows Beta to come with them, mumbling that they could "always use a set of spare parts." Not long after, Beta is basically torn apart and rebuilt into a very different robot for his rematch with Gamma.
302** Gamma's theme has a few words repeated throughout it. While they're distorted, it's possible to make out their meaning after listening closely, and they tie in with his story. Since the tune plays at various points during his story, including his very cutscene, it doubles as foreshadowing: [[spoiler:"It's my pleasure. Ready to die" foreshadows Gamma becoming a DeathSeeker late in his story upon realizing that he must destroy himself in order to free the animal contained within him.]]
303** When Gamma is ordered to retrieve the bird from Amy, the bird flies out of the cell and confronts it. A confused Amy wonders what's going on as Gamma releases her from her cell. [[spoiler:At the end of Gamma's story, the bird imprisoned inside it turns out to be a family member of the bird that Amy has]].
304** Upon bidding farewell to Gamma right before the destruction of the Egg Carrier, Amy promises that they will meet again some day. [[spoiler:Later in Super Sonic's story, we can see her accompanied by the Flicky that used to power up Gamma, indicating that they were reunited in a way.]]
305* FourLinesAllWaiting: Six main character storylines that both run alongside and intertwine with each other, with one overarching storyline that most of them loosely tie into (a vengeful monster has been released by the main villain, and is secretly pulling strings to eventually destroy the world).
306* FreeRotatingCamera: Not universal though.
307* {{Friendly Playful Dolphin}}s: Dolphins jump around you in Sonic's first stage, "Emerald Coast", if you're looking in the right place at the right time. The appearance of these dolphins and their numbers seems to be performance based, or it might be random.
308* TheFriendsWhoNeverHang: Only Sonic and Tails interact with all five other characters in the story, with Knuckles, Amy, Big, and Gamma never really meeting one or two. They can still occasionally find them as generic [=NPCs=] to assist in unlocking them, however.
309* FrigidWaterIsHarmless: Big's second stage is Icecap, which requires him to break through the ice in order to fish in its waters and catch Froggy. The fish living inside the water as well as Froggy are perfectly fine swimming inside it, and the only thing Big has to fear is drowning, especially if he didn't collect the Life Belt upgrade which allows him to swim before entering the stage. In the B and A Rank missions, Big has to swim through the secret passage under the water to get to a room where bigger fish required to complete the missions are stored.
310* TheGamblingAddict: One of the Station Square [=NPCs=] is a single mother who constantly abandons her young son to go to the casino. The son's dialogue reflects his constant distress over this.
311* GameBreakingBug:
312** Some of the game's glitches allow characters to access levels or parts of levels that they normally can't, and can also access stages out of order. However, doing this can cause glitches that, at best, make the level unbeatable, and at worst, make the ''game'' unbeatable. One of these is a bug that allows Knuckles to enter Casinopolis early. While you can play through the level without incident, the problem occurs when you beat it; Tikal whisks Knuckles away to the past... and he's stuck there. The game doesn't necessarily freeze, as Knuckles is still able to move around and explore, but Tikal and her father are glitched in a way that has them standing in midair. This prevents the cut-scene that ends this sequence from playing, making it literally impossible for Knuckles to ever leave the past.
313** The Crystal Ring is an optional upgrade that depletes the time it takes for Sonic's Light Speed Dash to charge. Most players grab it during their first session, but if you choose to collect it during Super Sonic's story, it will essentially ruin your save file. There is usually no auto-save point in Super Sonic's story, as it is just one long level, but acquiring the upgrade forces the game to save. That wouldn't be a problem, unless you have to switch off the console. Trying to reload the game will then lead to you seeing an otherwise-unused recap screen, before either being dumped in an inescapable Hedgehog Hammer room, a bottomless pit, or simply freezing the game altogether. Thankfully, bypassing this glitch if stumbled upon is as easy as simply beating a regular Action Stage, letting the game autosave and setup a proper load point after.
314** Windows will crash in certain times in ''DX'', most commonly during the fight with the Egg Hornet.
315** Since none of Big's levels feature BottomlessPits, glitching Big into falling into one (either by hacking the game to put him in such a level or glitching through the walls in the HubWorld) causes the game to crash during his death scream. This is fixed in the ''DX'' version.
316* GameMod: The 2004 PC version of the game has a dedicated modding community. Not only is there a mod loader that adds support for widescreen and custom resolutions, but mods exist that fix numerous glitches and add lost content back in (such as the DLC missions and holiday events). The Steam version can be made compatible with these mods through the [=BetterSADX=] or SADX Mod Installer tools.
317** The Dreamcast Conversion Mod faithfully restores nearly all of the textures, special effects, sounds, and level geometry of the Dreamcast version that were lost when the game was ported to other systems. The Lantern Engine mod also restores the Dreamcast's more atmospheric lighting, and yet another mod reverts the character models to their lower poly Dreamcast versions. There are also mods available that improve on changes in the ''DX'' version without replacing them with their Dreamcast counterparts.
318** A gameplay overhaul mod-hack making waves completely revamps aspects of the game by adding Shadow the Hedgehog, a better Metal Sonic, as well as an in-game Super Sonic and even Hyper Sonic. Sonic himself also gets a boost (a la ''VideoGame/SonicUnleashed'' onwards), a [[VideoGame/SonicAdventure2 bounce attack]], instant light-speed dash, and more. And that's just Sonic. [[https://www.youtube.com/watch?v=8ct1mYr06u0 It has to]] be seen [[https://www.youtube.com/watch?v=uYJ0xFX-2og to be believed.]]
319** The ''SADX Heroes'' mod is notable for bringing stages from ''VideoGame/SonicHeroes'' into ''Sonic Adventure DX''. These aren't truncated or redesigned stages either, but direct 1-to-1 lifts from ''Heroes'' into the ''Adventure'' engine with its gameplay and enemies (thus lacking the team gameplay mechanic). Interestingly, every stage can be completed despite lacking the team-based mechanics of ''Sonic Heroes''.
320* GameplayRoulette:
321** The gameplay style changes very frequently in Sonic's story. Outside of the series-standard platforming, there are a couple of pinball minigames in Casinopolis, snowboarding in Icecap, racing in Twinkle Park, and two different RailShooter segments.
322** The non-Sonic stories mix up the gameplay styles. Tails's levels have him race against Sonic (and, later, Eggman) to get to the goal first, Knuckles has to search segments of each level to find Master Emerald pieces, Amy runs from the robot [=ZERO=] with some stealth mechanics, Gamma does [[TimedMission timed]] run-and-gun sequences, and Big the Cat's story forgoes platforming almost entirely for a fishing simulator. For the most part, this is due to ''Sonic Adventure'' doubling as a sort of [[TechDemoGame tech demo]] of what the Dreamcast was capable of doing.
323* GameplayAndStoryIntegration:
324** There are some really neat examples where the intertwining storylines of each character affect the game itself. For instance, the reason Sonic's Sky Deck stage tilts all over the place in its third act? That's because Knuckles is required to switch the gravity around in his segment.
325** [[VirtualPet Chao]] who are properly cared for are granted BornAgainImmortality and come back to life as babies at the end of their life cycle, out of sheer love for their owner. This crops up in the game itself when we see that [[spoiler:Chaos' Chao friends have been successfully resurrecting through the years since Chaos was sealed -- and when Sonic returns him to his normal form, they finally get to play with their favorite caretaker again]].
326** Tails' stages have him race against other characters. When against Sonic, it's a friendly race, so if Tails falls too far behind, Sonic will stop and wait for his friend to catch up. However, when racing against Eggman, the good doctor has no such qualms about leaving Tails in the dust.
327* GameplayAndStorySegregation: In Gamma's Emerald Coast stage, he is inexplicably required to destroy Robotnik's badniks to complete the level, even though the level is set ''before'' his HeelFaceTurn.
328* GimmickLevel: Sonic's version of Casinopolis has a Chaos Emerald inside a large vault, on a platform that's too high for Sonic to jump onto. To reach the Emerald, you need to fill up the vault with 400 rings so the floor is high enough to jump off of, and to get the rings you need to play pinball (with Sonic as the ball) instead of platforming. Skilled players will know to intentionally lose a pinball game with under 100 rings in order to get to the sewer level, where it's much easier to rack up cash (this action is essential to complete the A-Rank mission, where Sonic has to destroy the capsule in under five minutes).
329* GoingThroughTheMotions: Not a major example, but quite noticeable in Amy's ending when she performs her boss victory animation and then abruptly snaps back to her standing animation.
330* GoThroughMe:
331** In the {{backstory}}, Tikal tries to defend the Chao and the Chaos Emeralds from her dad and his soldiers. Said soldiers brusquely push her aside and proceed to incur Chaos' wrath.
332** In the aftermath of Sonic's (or Tails') fight with Gamma, [[RashomonStyle regardless of who wins]], Amy intervenes to convince the victor to let the other live.
333* GrandFinale: The final story opens up after finishing the other ones, revealing the truth behind Chaos and wrapping up other loose ends.
334* GratuitousEnglish:
335** Sonic in Japanese sometimes speaks English with a [[JapaneseRanguage thick accent]], such as when he tells players to "Serect yo kaakta!" This became a defining trait of his character in later games.
336** Level names, location names, and upgrade names are in English in both versions.
337* GravityScrew: Most notably in Lost World, where panels on the wall glow when orientated correctly by hitting a switch, allowing Sonic and Knuckles to simply walk up the wall. The last part of Sky Deck changes orientation as well, and Knuckles can actually control this.
338* GrowingWithTheAudience: Prior to this game, the Sonic series was a fairly standard children's video game series in terms of setting and plot. With many of the original Sonic fans grown-up, this game decided to appeal to both older and newer fans with the new direction of the game. The art style took a more realistic bent, and the story dealt with more mature themes such as the genocide of an ancient race, the growing sentience of an otherwise robotic minion, and learning to stand up for yourself, with CharacterDevelopment for nearly everyone involved.
339* GuideDangIt:
340** The game has a few Adventure Field emblems that can be tricky to find. One of them in the Mystic Ruins requires flying over a large, seemingly empty space as Knuckles -- and the emblem itself ''won't show up because of the draw distance'' until you're actually close to it, so you wouldn't even think about jumping and gliding across that super large bottomless pit unless you somehow knew the emblem was there. Another one in the Egg Carrier requires you to fly on top of the giant spinning contraption at the back end of the ship's outside area as Tails, however the emblem is only collectible when the ship is in ''wings out'' mode that separates the front and back ends of the ship and allows you to enter the Sky Deck stage. You change the ship around by pressing a big red switch on the ground located in the control room near the giant spinning thing. Every time you come to the Egg Carrier after it's landed in the sea the ship is always set to ''wings in'' mode by default. It's so obscure to that even if you went up there the first time with the ship in ''wings in'' mode and found no emblem up there then you'd think that particular emblem was located somewhere else leaving you stumped until you finally looked up and found you have to transform the ship to make the emblem appear.
341** Most of the secret optional power ups/upgrades for all the characters, despite not being explained or shown in the manual, are not that difficult to find if you take time to explore the Adventure Fields (except for one upgrade for Big that is actually found in a secret area of Icecap). However, Amy's Long Hammer upgrade just takes the cake for this trope. In order to obtain it, you have to play the Hedgehog Hammer mini-game again after getting the Warrior Feather in the Adventure field (doing it from Trial mode in the game's menu will not work) and get a certain high number of points. On top of that, you have to play the mini-game after the Egg Carrier has landed in the ocean, so either go back there after killing Zero, or go back immediately after Tails drops you off in Station Square by taking the boat by the sea, and ''not'' immediately after getting the Warrior Feather. Nothing in the game ever hints at giving the Hedgehog Hammer another go after the Egg Carrier crashes, so many would have seen no point in playing the game again other than to get the emblem for it in Trial mode.
342** Amy's got another example that's more of a case of FigureItOutYourself. She's pigeon-toed with an overlapping gait and runs a lot slower than she would otherwise, so the way to get her grade A emblems is by getting her to take the biggest leaps possible as you move through her stages.
343** Chao raising in the original Dreamcast version is poorly explained. You can only see a Chao's stats, give them a name, and have access to all the different types of fruits if you transferred them into your VMU via the machine located in every garden. However, this is not explained by the game, nor its manual. The first game has a monitor in the Station Square garden hinting that different fruits have different effects on the Chao, but doesn't explain how to obtain them. There is also a Tikal hint orb which tells the player that animals can change the Chao's appearance, but omits the fact that it also affects the Chao's stats.
344* GustyGlade: Windy Valley, which serves as Sonic's second action stage, Tails' first, and Gamma's third. Sonic's section begins with him running through the lower parts of the valley until he reaches [[FunnelCloudJourney a tornado, which he must find his way out of]], ending with him running through the upper parts of the valley to get the Purple Chaos Emerald, which forms the entirety of Tails' section. In Gamma's section, Gamma travels through the lower parts of the valley to seek out and destroy E-103 Delta. Running through the strong winds will help you get across the large gaps over them.
345[[/folder]]
346
347[[folder:H-P]]
348* HailfirePeaks: Played straight in Sonic's levels (and a couple of Amy's), which frequently transition from one level type to another halfway through, often with some kind of setpiece to join them together. Mostly averted with the other characters, who stick to only one section of that level.
349** Windy Valley starts off as GustyGlade, then briefly becomes a FunnelCloudJourney when Sonic is sucked into a tornado, and once he emerges out of the top it becomes a LevelInTheClouds as he races through a series of metal walkways floating thousands of feet in the air.
350** Red Mountain starts off as DeathMountain until Sonic heads inside, at which point it becomes LethalLavaLand with a dash of FireAndBrimstoneHell.
351* HallOfMirrors: A segment exclusive to Amy's version of Twinkle Park.
352* HappyFlashback: The final screen of the game depicts Tikal playing with the chaos at the old Master Emerald shrine while a relaxed Chaos Zero watches over them all.
353* HeroicSacrifice: Before the events of the game, in order to [[spoiler:save the world from his destruction]], Chaos was sealed in the Master Emerald alongside Tikal.
354* HeroVsVillainDuet: The game's ThemeTune, "Open Your Heart," zigzags between the dark, monotone lyrics representing Chaos' perspective and the uplifting, determined lyrics representing Sonic's. In particular, the recurring instruction, "open your heart," is Sonic talking directly to Chaos.
355* HijackedByGanon: Inverted by [[spoiler:Chaos taking over the role of central villain from Eggman in the final story.]]
356* HintsAreForLosers: Touching one Hint Orb in Knuckles' B Rank missions disqualifies you from getting the Emblem.
357* HobblingTheGiant: Tails' storyline ends with a battle against the Egg Walker. To defeat it, Tails has to get underneath it to trick it into trying to stomp him. During this time, Tails has to attack its feet, causing it to lose its balance and giving Tails the opportunity to attack Dr. Eggman, who will then be low enough for him to attack.
358* HongKongDub: The lip-syncing is just plain bizarre and off a lot of the time. The MouthFlaps are mostly just looping animations without any consideration to the dialogue, so they don't even really match the Japanese track.
359* HopeSpot: Zig-zagged at the end of Amy's story. Birdie is reunited with his family, and everything seems okay... then suddenly ZERO shows up and swats Birdie out of the sky. After ZERO's defeat, Birdie wakes up and is seemingly okay, but as he flies off, he suddenly rapidly drops from sight... only to soar triumphantly back into view and fly off with his family in tow.
360* HostileAnimatronics: Downplayed. Casinopolis features some model ships crawling with animatronic pirates; while they can damage you like any other enemy, they never actively pursue you.
361* HubLevel: The game has three interconnected ones: Station Square, Mystic Ruins, and the Egg Carrier.
362* HundredPercentCompletion:
363** Getting all 130 emblems is the goal for fully clearing the game. Emblems are rewarded for beating each story, winning the minigames and the Chao races, finding them hidden in the Adventure fields, and clearing missions in each character's Action Stages. There are three missions for each stage, with the first being simply to finish it. The other two missions for each character are:
364*** Sonic: Collect 50 rings and clear the stage; clear it within an allotted timeframe.
365*** Tails: Collect 50 rings and beat Sonic/Eggman; beat Sonic/Eggman again (they're faster).
366*** Knuckles: Collect the emerald shards without any hints; collect them within an allotted timeframe.
367*** Amy: Same as Sonic's.
368*** Gamma: Collect 50 rings and destroy the target; destroy the target with a certain amount of time remaining.
369*** Big: Catch a 1000g fish and Froggy; catch a 2000g fish and Froggy.
370** There is no reward for collecting all the emblems in the original ''Sonic Adventure'' other than bragging rights, but in ''DX'', doing so will unlock [[spoiler:Metal Sonic as a playable character in Trial mode. He's essentially just a reskin of Sonic]].
371* IDieFree: Gamma's story rather morbidly invokes this when Gamma decides to rescue his E-100 series siblings by destroying them.
372* IWantSong: Tails's and Amy's themes: "[[IJustWantToBeSpecial Believe in Myself]]" and "[[StalkerWithACrush My Sweet Passion]]".
373* ICannotSelfTerminate: Played with during Gamma's story. Gamma is perfectly capable of self-terminating, it's just that up until the penultimate boss Gamma doesn't realize that his self-given mission technically ''requires him to kill himself''. The moment of contemplation concerning his mortality that he has when he realizes this is almost heart-breaking despite almost no dialogue or music being present in the scene. He ends up averting this trope and allows himself to die from his injuries so that the Flicky inside of him can be freed.
374* ICantBelieveImSayingThis: Knuckles says this, agreeing with Tails that Sonic is the only one who can harness the true power of the Chaos Emeralds after [[spoiler:Perfect Chaos]] absorbed their negative energy.
375* IOweYouMyLife: Not directly stated, but Gamma's resolve to rescue the animals trapped inside the E-Series robots was partly due to Amy saving its life (at least in Sonic and Tails's versions of the story; in Gamma's own story, she prevents it from killing Sonic instead, which further proves that Gamma is capable of empathy). Said act by Amy was also provoked by Gamma freeing her and Birdie from Eggman's cell inside the Egg Carrier (which would later crash land into the ocean) making it both issued and returned at the same time.
376* ISOStandardUrbanGroceries: The brown paper bag Amy carries in the introductory cutscene to her story.
377* IdiotBall:
378** All three incidents when Sonic and Tails lose Chaos Emeralds to Eggman. The third time this occurs, when two Chaos Emeralds are knocked out of Sonic/Tails's {{Hammerspace}} (depending on what character you're being) by a sharp impact. He then proceeds to ''sit there'' while Eggman lazily floats over and [[TractorBeam beams them up]]. Eggman lampshades this in the Tails vs. Knuckles storyline, where he calls them "bumbling idiots".
379** Knuckles, who has extrasensory perception of the Master Emerald shards, chases Eggman into a private room at the Station Square hotel because he immediately presumes the shiny object Eggman is holding must be one of the shards, without noticing that he hasn't sensed it like the others.
380* IgnorantOfTheCall: Tikal's attempts to guide the heroes by giving them {{flashback}}s of the past and teleporting them from place to place are fruitless -- most characters who encounter her have no idea what's going on, and immediately return to their own business once the vision ends. Near the end of his story, Sonic fails to get the message that he should go after Chaos instead of Eggman. This is likely because the flashbacks are more for the player's benefit than the characters.
381* ImplausibleDeniability: After Eggman seizes the two Chaos Emeralds dropped during Knuckles's fight with Sonic, Sonic demands to know if Knuckles was tricked by Eggman. In Knuckles's story, he blatantly dodges blame:
382-->"Like, you weren't?"
383* InCaseOfBossFightBreakGlass: The Egg Viper, but it gets harder as you go on.
384* IncomingHam: Eggman, Eggman, Eggman.
385-->"YOUUUUUUUUUUU KNOOWWWWWWWWWW NOTHING, [[YouFOOL FOOOOOOOOOOOOL!]] It's ''CHAOS! The GOD! OF DESTRUCTION!! [[EvilLaugh HAHAHAHAHAHAHAHAHAHAHA!]]''"
386* IndyEscape: At various points in Sonic's storyline, he has to evade the jaws of an angered orca, an avalanche and an ''Franchise/IndianaJones''-esque flaming boulder.
387* InsecureProtagonistArrogantAntagonist: Tails' story in the RashomonStyle plot explores his insecurities. While Tails is usually seen as a happy-go-lucky child, this game reveals that he feels guilty because he thinks he can't accomplish anything without Sonic doing it for him, and [[IJustWantToBeBadass he wants more than anything to be cool and self-confident like Sonic]]. He is contrasted by the BigBad, Dr. Eggman, an InsufferableGenius MadScientist who wants to control all of Station Square, the city where the game takes place. In the end, Tails saves the city by himself and drives Dr. Eggman to a VillainousBreakdown.
388* InsurmountableWaistHighFence: Right towards the end of Twinkle Park for Sonic, there's an iron gate blocking you from getting to a spring if you end up on the right side of it. You can barely jump higher than it by yourself and you can definitely jump higher than it if you get up some speed with a Spin Dash. However, the game won't let you pass it from that side, you have to circumnavigate the entire circular roof to approach the spring from the other side.[[note]]However, unlike other examples, this CAN be circumvented by simply jumping at the spring from one of the floating platforms leading to the roof. If you execute a homing attack at it, the game won't block your progress, which is good for the Emblem.[[/note]]
389* ItCanThink: Chaos spends most of the game as Eggman's personal minion, giving the appearance of a mindless monster...[[spoiler:but in Super Sonic's story, Chaos throws Eggman under the bus after suffering too many losses against Sonic and company, and he attacks Eggman to make him into a decoy to discreetly take 6 of the 7 Chaos Emeralds from an oblivious Knuckles for himself. He then goes after the one in the Tornado 2, allowing him to transform into Perfect Chaos and wreak havoc upon Station Square.]]
390* KaizoTrap: The Egg Viper has a nasty trick up its sleeve when Sonic completely depletes its HitPoints--as it flails about, it will make a last-ditch attempt to ram the platform Sonic is standing on. The camera angle isn't great either, so even if you know his suicide attack is coming, you won't be able to tell where he's gonna hit so you may still die anyway. And beware of losing too many platforms, because the Viper will take you down if it's the last platform remaining.
391* KarmaHoudini: Perfect Chaos, the TrueFinalBoss, who, while defeated and rendered docile in the end, still destroyed Station Square and by rights should have killed thousands of people. He gets an utterly unironic HappyEnding.
392* KarmicDeath: Implied. In the past, [[spoiler:Chaos absorbed the Emeralds to transform into Perfect Chaos]], wiping out Pachacamac and the echidnas for all of their careless warmongering.
393* KickTheDog:
394** Eggman does it a ''lot'' in this game. He's portrayed as a lot more evil here than in most portrayals.
395** In the flashback of the final story, Pachacamac ordered the echidna warriors to charge to the Emerald shrine, [[spoiler:trampling Tikal and injuring the Chao]], just so they can seize the Chaos Emeralds. [[spoiler:Chaos didn't take kindly to this]].
396* KillItWithIce: Sonic and Knuckles battle Chaos 6 on the deck of the Egg Carrier. Dr. Eggman tosses freezer bombs, intending to use them to freeze Sonic or Knuckles, but the two can use them to freeze Chaos 6 by tossing them at him or tricking him into sucking them up with his VacuumMouth. Once Chaos 6 is frozen, Sonic or Knuckles can jump on him to damage him.
397* KnightOfCerebus: Chaos. He is the first major threat Sonic and co. face that has ''no'' humorous quirks or traits whatsoever in persona and design; while his threat is genuine, he isn't seen as much more than a [[TheDragon Dragon]] to Eggman [[spoiler:until the climax and finale, when things truly take a turn for the worse when he finally turns on Eggman and gets all of the Emeralds.]]
398* LastBreathBullet: The defeated E-101 mk.II gets in one last shot at Gamma before exploding; the shot fatally wounds Gamma and he too is destroyed shortly after.
399* LastNoteNightmare: "Fakery Way" for Amy's section in Twinkle Park starts out in a quiet, cute tone, but slowly becomes much more creepy and menacing.
400* LastOfHisKind: Knuckles is the only echidna alive. [[spoiler:Though Tikal's spirit lingers around after being released from inside the Master Emerald.]]
401* LeftStuckAfterAttack: This is what makes the Egg Hornet a TacticalSuicideBoss. It's normally out of reach, but one of its attacks has it sprout a pair of spikes and try to ram you with them. This leaves it stuck in the ground for a moment, and wide open to attack.
402* {{Leitmotif}}: Every character is accompanied by their theme tune when they appear.
403* LensFlare: Present in some of the cutscenes, as well as Emerald Coast and Sky Chase Act I.
404* LethalLavaLand: Red Mountain, [[HailfirePeaks combined with]] some DeathMountain. This stage serves as Sonic's seventh action stage, Knuckles' third, and Gamma's fourth. Knuckles' section has him search for the pieces of the Master Emerald around the outside of a massive volcano, while Gamma's section has him go inside the volcano to seek out and destroy E-104 Epsilon. Sonic's section consists of elements from both Knuckles and Gamma's sections, as he is first outside the volcano and must find a way inside, then must find a way out of the volcano so he can meet up with Tails.
405* LetsYouAndHimFight: Eggman tricks Knuckles into fighting Sonic for the second time (or Tails if you play as him).
406* LevelsTakeFlight: Sky Chase reappears with two acts, and allows Tails to actually fire upon incoming enemies with his Tornado's machine guns and missiles.
407* LittleNo: Sonic shouts one of these any time he dies.
408* TheLoad:
409** Tails generally achieves nothing worthwhile when he tags along when you play as Sonic, and he becomes [[TheMillstone outright detrimental]] if you're hunting down specific animals because of his tendency to run into the path of them and pick them up. Before ''DX'', his movements followed the player's button inputs and usually lead to him going astray very quickly, and there was no way of disabling him. He tags along with Sonic as much as he can in ''DX'', but in both versions he struggles to attack enemies and is often caught up in and immobilised by Sonic's own attacks.
410** This extends to his storyline. When they're both separated, Tails feels inadequate because he's only ever useful with Sonic around, though he figures out he can act on his own. It culminates with him deactivating the missile threatening to blow up Station Square, then defeating Eggman's Egg Walker without Sonic helping.
411* LongSongShortScene:
412** A few jingles and themes were unused in gameplay or for purposes different from how they are labelled (eg. "Calm After The Storm" is labelled as the theme for the crashed Egg Carrier Adventure Field in the Sound Test, but is used only in a short cutscene in Gamma's story). Many tunes were also truncated and can only be heard in full in the games' official soundtrack.
413** Subverted with the "Leading Lights" theme for Lost World. Playing through Sonic's story, it will only play in Sonic's third "act" of the level...a single room where the level ends after literally taking just a few steps. Once you play through Knuckles' version of Lost World though, you'll hear this song again, and this time it will finally get the playtime it deserves.
414** The character battle theme "Fight For My Own Way" is only heard in fights that take less than 10 seconds to complete for most players due to the opposing characters' ArtificialStupidity. One would have to actively hold back in order to hear more than the intro. Same goes for "Heartless Colleague", which plays in the similarly brief bouts with the E-Series robots.
415* LoveTriangle: A couple standing at the elevators at Station Square's hotel are arguing after the woman has discovered that her boyfriend is seeing another woman. Eventually, both women and the man are seen arguing at the swimming pool.
416* MacguffinDeliveryService: Sonic and Tails don't do that great a job of keeping the Chaos Emeralds away from Eggman and Chaos.
417* MagicIsFeminine: Tikal, the princess of the Echidna tribe and the only definite female member that we see in the game, is the only one who lives in harmony with the mystical Chao. Tikal also mentions that her grandmother was the one who taught her about the Chao. The other tribe members, who seem to be all male, try to destroy the Chao and their shrine, only to accidentally anger and summon Chaos, the mythical protector of the Chao, who destroys them all.
418* MalevolentArchitecture: Speed Highway, a highway that uses loop-de-loops, corkscrews and ''has gaps missing'', all while being high in the air.
419* MaliciousMisnaming: Sonic addresses Knuckles as "Knucklehead" for the first time.
420* MamaBear: Amy to Birdie. In one instance, she adamantly refuses to give Birdie to Gamma, which then led to his change of heart. In the other instance, which stands out more, Amy was [[BerserkButton enraged when [=ZERO=] knocked Birdie out cold]] and was very keen on bashing him with her hammer.
421* ManiacMonkeys: Kiki is a robotic monkey who serves as a common enemy. He [[MadBomber tosses bombs]] that can be picked up and thrown at other enemies, but they explode quickly, so you'll need to throw them fast.
422* {{Mayincatec}}: {{Defied|Trope}}; Sega paid a few developers around $250,000 ''each'' to go down to Mexico and do research on Mayan culture for the game. Consequently, the Mystic Ruins -- and by extension, Sand Hill and Lost World -- are very distinctly based on the Maya rather than using a generic Mesoamerican aesthetic, which carries over onto Tikal (who herself is named after an ancient Mayan city in what is now Guatemala) and the rest of the Echidna Tribe.
423* MeleeATrois: By the end of the game, Chaos no longer abides by Eggman's repeated failures to feed it Chaos Emeralds and lashes out, trashing Station Square and absorbs all the Emeralds' power on its own. Eggman knows he screwed up so he attempts to stop Chaos himself but only sees his latest Egg Carrier destroyed. Then Sonic steps in, takes what positive energy remains in the Chaos Emeralds, turns Super, and deals with the problem.
424* MercyLead: A black Chao named Chacron will sometimes appear in Chao Races. Unlike the other racers, it will idly lounge at the starting line once the race starts. You will soon find out that this is a mercy lead, as once one of the other Chao is halfway through the race, it will get up and take off at a ridiculously high speed, very easily overtaking the other racers unless they have high stats themselves.
425* MetropolisLevel: Speed Highway is a level taking place within the bustling heart of Station Square. It starts off with loop-de-loops on highways and precise platforming across the city skyline before transitioning to the main plaza on ground level via running down a building. Hazards include cars to avoid and Eggman's Badniks mimicking the police.
426* MisplacedRetribution: Chaos' anger at the abuse of the Chao he used to protect leads him to work towards the destruction of Station Square, even though the people of the city had absolutely nothing to do with the incident and weren't even alive at the time. Indeed, by all indications, the people of Station Square genuinely care for Chao.
427* MissingSecret: Gamma's story recap before heading to Emerald Coast says that he must equip "S-type armor" to proceed. There is no such upgrade, and it's never mentioned outside of this text.
428* MistreatmentInducedBetrayal: While Gamma himself is treated well, Eggman's treatment of the ''other'' E-100 robots and the animals that power them leads him to decide to turn on his creator.
429* MyGodWhatHaveIDone: Gamma begins to feel remorse in his story recap after he releases Amy and Birdie and disobeys his master's orders.
430* MythologyGag:
431** The music for Twinkle Park's hovercraft and Windy Valley's "The Air" segments are remixes of the Panic Puppet and Green Grove themes from the Genesis version of ''VideoGame/Sonic3DFlickiesIsland''. Twinkle Park's "Pleasure Castle" stage is a remix of [[https://www.youtube.com/watch?v=WW25LsLmOTs an unused theme]] from said game, too, though this wasn't known until years after the fact. Also, the second part of Emerald Coast has a MusicalNod to the first boss theme from that game. Jun Senoue, the composer for both games, [[https://www.sonicnotes.info/1999/01/jun-fumie-twinkle-cart-sonic-adventure-soundtrack-comment.html stated on the official soundtrack]] that he included these nods because the Genesis version of ''Sonic 3D'' never got released in Japan and he didn't want his work to go to waste.
432** The Speed Shoes music uses the opening sound effect of the title theme from ''VideoGame/SonicTheHedgehogCD'', while the Invincibility music quotes "You Can Do Anything" from the same game.
433** In Sonic's Casinopolis stage, you can use Sonic as a pinball, just like [[VideoGame/SonicTheHedgehog2 Casino Night Zone]], among other examples.
434** Several to [[Anime/SonicTheHedgehogTheMovie the OVA]]. The logo sequence in the opening FMV is a reference to the logo sequence in the OVA, even using the same sound effect. The Tornado launch sequence was taken from the OVA as well, along with the idea of Knuckles being a treasure hunter. The depiction of Station Square as a flooded city in ruins at the end was inspired by the ancient city ruins in the OVA, even using much of the same imagery.
435** "Leading Lights" sounds very similar to [[VideoGame/Sonic3AndKnuckles Mushroom Hill Zone]] in parts.
436** Play the Samba GP DLC as Sonic and you'll be treated to an instrumental rendition of "Super Sonic Racing" from ''VideoGame/SonicR''.
437** The Y2K Celebration DLC adds giant Rings to Station Square and Emerald Coast reading "Millennium 2000 Welcome!" Touching them changes the background music to the Japanese/PAL version of [[VideoGame/SonicTheHedgehogCD "Palmtree Panic Zone (Present)"]].
438* NeverSayDie:
439** [[AvertedTrope Averted]]; talk to [=NPCs=] during Tails' story after Eggman sets off his missile, and they'll all be panicking over how they're about to die.
440** Gamma's theme sneaks in the repeated phrase "It's my pleasure. Ready to die." It is so distorted and eclipsed by the instrumentals that any censors would have missed it.
441* NiceJobBreakingItHero: Knuckles being tricked into fighting Sonic led the two colliding with each other. As a result, Sonic fumbles the two remaining Chaos Emeralds (one of them being green which Knuckles ''thought was a piece of the Master Emerald''), only for Eggman to steal them and power up Chaos into his fourth form. As Sonic best puts it:
442-->'''Sonic''': Smooth move, [[{{Pun}} knucklehead]]!
443* NiceJobFixingItVillain:
444** Sonic and Knuckles have no way to defeat Chaos 6, but luckily Eggman provides both with ice-spewing egg robots onto the battlefield that both can use to freeze Chaos and hit him.
445** E-101 Mark II fires one last shot at Gamma before exploding, killing them both and releasing their Flickies.
446** Eggman's mistreatment of the E-Series and Amy played part in Gamma's HeelFaceTurn. In Gamma's own story at least, had this not occurred, he would have destroyed Sonic for him.
447* NoEndorHolocaust: Downplayed. The {{True Final Boss}}'s big entrance into the city completely razes Station Square, which by rights should have killed thousands of people or more. The cast universally chooses to not talk about the body-count while standing amidst the wreckage. Tails even puts in a cheerful, "All's well that ends well," afterwards. The ''Anime/SonicX'' adaptation addresses this by depicting the evacuation and subsequent clean-up.
448* NoOSHACompliance:
449** Station Square is a death trap, boasting a highway with loops and a pleasure park containing floating platforms and a hall of mirrors where the flooring tends to give way beneath you.
450** Eggman would be in trouble if a safety inspector took a good look at the Egg Carrier's Sky Deck.
451* NobodyPoops: Surprisingly averted. One Action Stage (Hot Shelter) contains men's and women's restrooms, both of which can be entered, though not used. Which is odd, since it's inhabited solely by Eggman and his army of robots.
452* NonIndicativeName: Some of the levels as other characters, who only play in certain parts of them:
453** Casinopolis as Tails takes place entirely in the sewers.
454** Speed Highway as Knuckles features essentially none of the highways and much less speed, due to being an emerald hunting stage in the lower streets of the city.
455** Gamma's Final Egg is his ''first'' level.
456** The Western releases of ''Sonic Adventure DX'' has the added subtitle of "''Director's Cut''", which doesn't make sense as Takashi Iizuka, who directed the original version of the game, is not the director of ''DX'' version of the game; instead, it was directed by Kenjiro Morimoto.
457* NonLethalKO:
458** Big the Cat loses a life if he breaks the line on his Fishing Rod.
459** Gamma loses a life if the time runs out, implying that he's running on battery power.
460** Tails loses a life if he loses a race to his opponent. This makes ''some'' sense in his final Action Stage, where he races against Eggman in order to disarm a giant missile, but in all his other Stages, he's in a friendly race against Sonic to obtain a Chaos Emerald. Plot-wise, since both Sonic and Tails are collecting the Emeralds simply to keep them from Eggman, it shouldn't matter who touches them first.
461* AnOddPlaceToSleep: Big lives in the Mystic Ruins jungle, in an open hut shaded by a single palm tree. His bed is shaped like a normal bed, but made out of wood. Behind the head of the bed is a rack where three of his rods hang. Under the bed is a very shallow storage area he's carved out, which he can access by merely pushing the bed to one side; the Power Rod upgrade is located here. To the left of the bed is a tree stump he uses as a table; an empty wooden bowl sits on it. Hanging above the bed is a lantern that is always lit, although it's unclear if the light is a flame, or Big has somehow managed to get some source of electricity to power it. In front of the foot of the bed is a small set of steps (five, to be exact) leading to a very shallow stream. And, to top it all off, next to the steps is a homemade '''mailbox'''. That's right. Big has a mailbox. Tails's workshop doesn't even seem to have a mail '''slot''' on the door, and it's located right next to the train station!
462* OffscreenMomentOfAwesome: Somehow, Big managed to fly Tails' highly advanced Tornado plane back to his home with zero experience. Sadly we only see a brief clip of him taking off from the Egg Carrier in it. No Sky Chase minigame for you, Big.
463* OffscreenTeleportation: ZERO in Amy's levels.
464* OffscreenVillainDarkMatter: Eggman was somehow able to build a ''second'', fully functional Egg Carrier right alongside the original, just in time before the final battle.
465* OhNoNotAgain:
466** Knuckles says this when he is sent in a flashback in the past for the third time. Also, Sonic says this in his story after encountering Chaos, who has transformed into his 6th form.
467** If you fail at Sky Chase Act II, the Tornado will spiral downward in the same way it did after completing Act I. Tails even screams "Not again!"
468* OneWingedAngel: Chaos becomes his final form, [[spoiler:Perfect Chaos]], after he drains the negative energy out of all seven Chaos Emeralds.
469* OOCIsSeriousBusiness: In the cutscene before the Egg Walker boss fight, Eggman, normally a loud and flamboyant LargeHam, drops his usual theatrics and bluntly threatens tails in full TranquilFury mode. The contrast to his usual boisterous demeanor is downright ''chilling'' and shows just how displeased he is at these developments.
470* OutsideGenreFoe: In almost all of the previous ''Sonic'' games, the threat always came from Eggman and his machines, and he simply intended to use the Chaos Emeralds as a means to an end. Chaos is the first major villain in the series to rely entirely on mystical powers instead of the threat of science and machinery to achieve his goals [[note]]The sole exception in the earlier games was Witchcart, a [[VillainOfTheWeek throwaway villain]] from ''VideoGame/TailsSkypatrol'' who could trap people in crystals.[[/note]] and unlike the [[CardCarryingVillain black-and-white morals of Eggman]], Chaos is driven by a vengeful rage to use his power to destroy the entire planet. Even Eggman is left at his mercy when he reaches his full power. He is also the first character in the series to have explicitly killed another character—specifically, [[spoiler:he drove the entire Echidna race to near extinction]].
471* PalmtreePanic: Emerald Coast. Bonus points as the 2000 Millennium DLC changes the music of this stage to the TropeNamer. This stage serves as Sonic's first action stage, Gamma's second, and Big's third. In Sonic's section, Sonic searches the beach for Tails after he crash-lands, in Gamma's, he seeks out Froggy in the first part of Sonic's section, and in Big's, he fishes for Froggy near the lighthouse that leads to the second part of Sonic's section.
472* PalsWithJesus: Tikal is friends with Chaos, God of Destruction.
473* PapaWolf: Chaos to Tikal and the Chao, as the echidnas learned the hard way when they [[spoiler:attacked the Chao living at the Master Emerald shrine]].
474* ParentService: The original 1998 Japanese release includes a risque cowgirl billboard in the Casinopolis stage. The cowgirl even ''moans'' when one of the playable characters touch it.
475* PathOfGreatestResistance: Ever since ''Sonic Adventure'' introduced the Homing Attack, nearly all ''Sonic'' games since then have had paths identifiable (and accessible) only by finding a trail of stationary midair enemies. This is most commonly used to begin an expert path or for a shortcut; very rarely is it actually required.
476* PatternCodedEggs: The Chao are virtual creatures that can be raised in Chao Gardens and used to compete in races to win emblems. While the standard Chao eggs are white with light blue spots (as the standard Chao is light blue), other Chao eggs are the same color as the Chao inside them. Such examples include the Gold, Silver, and Black eggs that can be found hidden in the adventure fields, and the rare eggs that can be bought on the black market in the ''DX'' remake of the game and the ''Battle'' remake of ''VideoGame/SonicAdventure2''.
477* PensieveFlashback: Tikal's M.O. for giving the playable characters {{Exposition}} on the backstory of Chaos and the ancient Echidna civilization.
478* PinballZone: Sonic's version of Casinopolis features ''Sonic'' and ''VideoGame/{{NiGHTS|Into Dreams}}''-[[ShoutOut themed]] pinball tables. Naturally, Sonic himself is the pinball.
479* PlayableEpilogue:
480** You can still play each character's story mode (except the final story) after you've finished it, and the NPC dialogue will reflect this. Besides [=NPCs=] gaining new dialogue, you can find a card key to unlock Twinkle Circuit for characters who didn't visit Twinkle Park in their story. Mission Mode in ''DX'' also seems to take place after the main story.
481** This creates some minor continuity errors for Amy, who still has Birdie with her, and Gamma, [[GameplayAndStorySegregation who should be dead by the end of his story]]. It's likely that their "epilogues" instead take place shortly before their final bosses; unlike the other characters, Gamma's epilogue takes place at night in the Dreamcast version.
482* PlotCoupon: The Chaos Emeralds and finding them is the main focus of the story for both the heroes and the villain.
483* PlotTunnel: There are certain points in each character's story where they will be locked into a certain adventure field, and cannot leave to go to another. Most notably is the train strike that prevents the player from traveling to the Mystic Ruins from Station Square, and vice versa. This is especially apparent in Sonic and Tails' stories, where the strike will keep the two separated and prevent them from meeting back up until later on in the story.
484* PoliceAreUseless: Station Square's police force tries to shoot Chaos 0, but being [[MakingASplash a water monster]], all their bullets go right through him. Upon discovering this, they immediately retreat. This would be justified... except that Chaos has a [[AttackItsWeakPoint blatantly obvious weak point in the form of its brain]]. You'd think they'd at least try shooting there.
485* PooledFunds: Inverted; in Casinopolis, there's a Chaos Emerald in a vault that's too high for Sonic to reach normally, so he builds a pile of 400 Rings to ''walk across'' and grab it.
486* PoorCommunicationKills: Rather than talk to Sonic and Tails about why he's after the Master Emerald shards, Knuckles instead immediately starts a fight with them. Heck, if he'd just been more specific about what he was after, that would have been enough for Sonic to realise the misunderstanding and clear it up.
487* ThePowerOfFriendship: The bond of Sonic with his TrueCompanions allows him to unlock the full potential of Super Sonic with the Chaos Emeralds; Chaos had only absorbed the negative energy of the Emeralds, allowing Sonic to use the positive energy.
488* ThePowerOfLove: The song playing through the above, "Open Your Heart", also suggests it works as this.
489* PreRenderedGraphics: The opening cutscene before the title screen, Angel Island falling, most scenes involving the [[CoolAirship Egg Carrier]], and [[spoiler:Perfect Chaos]]'s introductory cutscene are all pre-rendered. The remaining cutscenes are done in-engine.
490* ProductPlacement: The competition-based DLC packs were sponsored by companies like Reebok and AT&T. The Reebok challenge even had you picking up Reebok sneakers that were strewn about Emerald Coast. There was also a Japan-exclusive DLC mission that had you collect QUO cards.
491[[/folder]]
492
493[[folder:R-Z]]
494* RacingMinigame:
495** Twinkle Circuit, a short race course included as part of the Twinkle Park experience. Sonic, Amy and Big can play it as soon as they have access to the area; everyone else has to wait until they complete their story modes. It's purely a time trial, with the objective being to complete three laps as fast as possible; each character's cart also performs differently, something the game never mentions.
496** All five of Tails' action stages have him racing against Sonic (and in the case of the last level, Eggman). The B Rank missions require him to reach the goal with at least 50 rings, and the A Rank missions require him to beat a faster Sonic (or Eggman).
497** The hotel of Station Square has a stadium within its Chao Garden, where you can enter the Chao you raised in races against other Chao. The animals and fruits you give your Chao will increase its stats.
498* RageBreakingPoint:[[spoiler: Amy hits hers at the end of her story. After ZERO has spent the game chasing her, the moment it attacks her bird friend, the MamaBear comes out and Amy destroys it.]]
499* RaisingSim: The Chao Garden, which can still be done even when the main story is completed.
500* RandomEventsPlot: Big's story has nothing meaningful to do with any of the other protagonists' stories. He has zero interest in the conflict over the Chaos Emeralds (he doesn't even know what they ''are'', thinking the one in his possession is just a simple gem that he considers a lucky charm) or the threat Chaos poses. He only intersects with the other protagonists completely by chance during his quest to rescue Froggy, who himself only gets entangled in the mess thanks to consuming a Chaos Emerald and acquiring Chaos' tail and thus drawing the attention of Dr. Eggman. No one even learns Big's name at any point.
501* RashomonStyle:
502** Who won in the character vs. character fights? It depends who you ask. Most of the dialogue was re-recorded for each story even when it doesn't need to be.
503** In Sonic and Tails's stories, the character played as is the one who fights most of the bosses and puts the keys in the Mystic Ruins. Chaos 4 is also apparently fought simultaneously by Sonic, Tails, and Knuckles, with the actual combatant being the one you're currently controlling. Chaos 6 is fought by Sonic and Big simultaneously but then Knuckles arrives after Sonic gives chase to Eggman and definitively defeats Chaos 6 in his own battle.
504** Also applies heavily to the dialogue in cutscenes that appeared in multiple characters' storylines. Though the general meaning of what's said stays the same, the exact words will often be different (though this doesn't occur in the Japanese version) and sometimes, which character says what will get switched around. Most notably, it occurs in Tails' story, which has large sections that overlap with Sonic's; many of Sonic's lines from his story are given to Tails instead, and most of Eggman's lines sound noticeably more menacing to reflect how the young fox is more intimidated by him.
505* RecurringBoss:
506** Chaos 4 is fought by Sonic, Tails ''and'' Knuckles in each of their stories, and Chaos 6 is fought by Sonic, Knuckles and Big in their playthroughs as well (though Big's fight is completely reworked to focus on his fishing mechanics). For Knuckles and Big, Chaos 6 is also the final boss of their stories.
507** Dr. Eggman's Egg Hornet is also fought twice in the game, by Sonic and Tails very early in their stories.
508** As for E-101, he's the first and last boss fought by Gamma in his story. The first fight is after completing Gamma's intro stage, while the second and last is the last boss in the playthrough.
509* RecurringExtra: There's [[https://twitter.com/SPEEPSHighway/status/1062510404029571074 an old man]] in Station Square who only ever appears in the scenarios' non-playable intros and endings, including in plain view from behind on Amy's ending screen.
510* RhinoRampage: Rhinotank is a robotic rhino who inhabits Emerald Coast and Windy Valley. He moves around terrain, but when he notices the player, he starts charging towards them in a straight line.
511* RidiculouslyCuteCritter: This game introduced Chao to the series, which are little cartoon creatures with an antenna-like shape-shifting orb floating over their heads.
512* RoboSpeak: On paper, Gamma speaks like this, using stock phrases like "Insufficient data," and "Does not compute," but his voice is more of a smooth and suave baritone than purely MachineMonotone. In the Japanese text, his dialogue is spelled mostly through katakana, as well.
513* RodAndReelRepurposed: While Big the Cat does use his fishing rod primarily for fishing, he can also use it to attack enemies from a distance if he aims it at them. He can also use his fishing rod as a club if he is standing next to an enemy.
514* RubberBandAI: Most of Tails' levels involve racing against Sonic, who is controlled by an AI trying to complete the course via the "normal" path while Tails has access to shortcuts via flying. The AI won't outpace you too hard if you trail behind, but will also warp across the level to catch up if you go too far ahead. [[https://www.youtube.com/watch?v=8DLzQfLBw-w Even skipping whole sections of a level won't do any good.]]
515* TheRuinsICaused: The team looking down upon [[spoiler:the flooded Station Square after purifying Chaos]].
516* RuleOfThree: Tails' and Knuckles' stories has three bosses, the goal of Knuckles' stages is to find three Master Emerald Shards, Knuckles gets a vision of the past on three separate occasions (whereas the other five characters only get one), Amy's storyline has three levels (the fewest level count any character has in this game), and three of Gamma's levels focus on hunting down the rest of the E-100 Egg Carrier crew.
517* {{Sampling}}: [[https://www.youtube.com/watch?v=K4FLexYgadg "Red Hot Skull"]], the theme that plays in the underground section in Red Mountain, samples its drumbeat from a Hip-Hop remix of "Ghetto Red Hot" by Super Cat (the [[https://www.youtube.com/watch?v=s98VjXtBSvo instrumental version]], to be exact).
518* SayingSoundEffectsOutLoud: E-102 Gamma says "pick up," "put down," and "throw" out loud when handling objects (or Chao).
519* ScaryScorpions: Chaos 6 takes on the form of a bloated scorpion, and one of his attacks against Sonic, Knuckles, and Big is stinging them with his tail.
520* SceneryPorn: It may look a bit dated now, but it was considered highly impressive back then when put side-by-side with games on the Platform/PlayStation and Platform/Nintendo64. Unfortunately, ''DX'' ruined a number of the textures and scenery and every further port decreased the quality more.
521* SealedEvilInACan: Chaos was originally sealed in the Master Emerald along with Tikal, but in modern times, Eggman freed him by destroying the Master Emerald. [[spoiler:As it turns out, Tikal deliberately sealed herself with him to prevent him from doing any more damage after the Echidna Tribe attacked the Master Emerald's altar. It also turns out that Chaos isn't actually evil, just very angry and vengeful.]]
522* SealedGoodInACan: Tikal was sealed in the Master Emerald along with Chaos.
523* SelfDeprecation: Surprisingly, ''Big'' has a subtle bit of this near the end of his game, after rescuing Froggy from the Hot Shelter. Naturally, though, this is just before Sonic offers him a helping hand.
524-->'''Big:''' If something happens now... There's no point to my rescuin' you. I don't know who would bother to rescue us both.
525* SelfServingMemory: While it's not mentioned in the game itself, the official strategy guide gives this as the reason for any differences between the character's stories.
526* SequenceBreaking: ''Sonic Adventure'' has plenty of glitches of its own, enough for sequence breaks to be prevalent.
527** By knowing where to continuously jump at with Tails, you can glitch behind the wall at the hotel pool. From there, you can fly over to Casinopolis and complete it. However, because the doors from Casinopolis will remain closed [[NoFairCheating if you didn't unlock it]], you may need to do another glitch to leave.
528** Sonic's version of Casinopolis can be beaten within 15 seconds if you jump the right way and glitch through a wall to retrieve the Chaos Emerald.
529** Final Egg with Sonic can be finished in under a minute. The first section of the stage has no real glitches, however the second section can be bypassed by getting inside the rotating fan which will not deactivate the death box allowing you to finish it stupid early. The third and final section is the worst. You can spin dash through a nearby wall behind the spider elevator, sending you into complete darkness, however if you steer correctly, you'll send Sonic falling down onto the end platform and finishing the stage.
530** Red Mountain has a large portion that can be skipped by less than 30 seconds in, Sonic can Spin Dash towards a rock on what appears to be a false wall which turns out to be real, then Spin Dash around this wall after landing on said rock and you'll put yourself near the entrance of the mountain. This can be broken further by activating the event lava rise box by glitching Sonic high enough to get the lava to rise to its highest height, bypassing the entire stage.
531** If you glitch correctly in Icecap with Sonic, the first section can be finished nearly in 5 seconds, the second section can be glitched right away through the large wooden door you have to find a way to open by running around, and you can glitch through a wall near the snowboarding section, allowing Sonic to run down the mountain instead, but he'll never activate the timer again, meaning that whatever time it said at the end of the second section of this stage is the time that'll finish when you reach the end of the stage regardless of how long it took.
532** Twinkle Park can be glitched as well with Sonic to allow for heavy sequence breaking. If you maneuver Sonic right, you'll skip the roller coaster. Go a step further and you can put yourself with a good Spin Dash jump right near the end of the stage.
533** A correct Spin Dash jump on Speed Highway can skip the last 30% of the first section. Another Spin Dash jump on the final section can throw you over the buildings to the exit, meaning Sonic doesn't have to run around them and waste any time.
534** If one does a good Spin Dash jump, they can skip the majority of the tornado simply by jumping in the right direction and landing on a spring, skipping the bridge and the trampoline.
535** Another good Spin Dash jump can bypass the entire final section of Sky Deck where the ship turns sideways. The player can put themselves right at the spring. If you can hit it before the ship flips entirely, you can actually finish the stage without having to monkey-bar around, then flip the ship back to a normal gravity.
536** Lost World can also be glitched with Sonic. A correct Spin Dash jump can throw Sonic through the door at the snake pool, bypassing the switch pressing section. The player has to perform this while standing on the stone snake head outside the snake pool.
537** While the most typical way of unlocking characters is to encounter them in Sonic's story, this isn't necessary. You can unlock characters after encountering them in any other character's story, leading to unusual situations like unlocking Amy after E-102.
538** It accomplishes exactly nothing but you can grab the Crystal Ring as soon as you leave Emerald Coast for the first time by hitting the button at the top of the stairs then getting over to the door above the hotel desk fast enough (which isn't very difficult, just precise), skipping the need to Light Dash to it. However you won't be able to use it until you get the Light Speed Shoes after Windy Valley.
539* SequentialBoss: [[spoiler:Perfect Chaos]] is a two-stage boss fight, with separate life bars for each stage. The second stage is identical to the first except that [[spoiler:Perfect Chaos]]'s theme plays instead of "Open Your Heart", and its attacks are a lot nastier.
540* ShootingGallery: Gamma's section of Final Egg has Gamma partake in one of these, with the goal of the level being to destroy a stuffed doll of Sonic. Destroying stuffed dolls of Tails and Knuckles adds extra time to Gamma's time limit.
541* ShoutOut:
542** [[VideoGame/NightsIntoDreams NiGHTS]] appears in their own pinball stage in Casinopolis, and the Flying Chao is shaped like them.
543** A section of Lost World has you [[Film/RaidersOfTheLostArk being chased by a boulder]].
544** At one point, Gamma says "[[Franchise/StarTrek Resistance is futile.]]"
545** Amy's intro cutscene has a bag marked "YU-2 Mart". YU-2 was what Yuji Naka was credited as in the Genesis ''Sonic'' games.
546** The E-100 Elite crew consists of [[Franchise/TeenageMutantNinjaTurtles four individuals with the colour scheme of red, blue, orange and purple]]. If counting the green Zero and the black E-101, and substituting pink with purple, it can also be seen as a shout-out to ''Series/KyoryuSentaiZyuranger'' (a.k.a., the original team of ''Series/MightyMorphinPowerRangers'').
547** The "Red Hot Skull" music from the underground portion of Red Mountain is incredibly similar in some parts to the "Crying World" theme from Planet Automation in ''VideoGame/{{Ristar}}'', an earlier Sonic Team game.
548* ShowerScene: Possible in Casinopolis with Sonic if you have him stand under a showerhead, whereupon he'll start scrubbing himself. Knuckles can also trigger the water spray, but he has no custom animation for it.
549* SlippySlideyIceWorld: Icecap, which serves as Sonic's fourth action stage, Tails' third, and Big's second. Sonic's section first has Sonic make his way into in an icy cave, then find his way out of it, ending with a segment where he rides a snowboard to outrun an avalanche, which forms the entirety of Tails' section. Big's section has him search for Froggy in the icy cave, breaking the thin ice by tossing boulders onto it.
550* SmokeOut: Eggman employs a variety of these tricks, including a flash grenade and sleeping gas.
551* TheSmurfettePrinciple: Out of the six playable characters, Amy is the only girl, though [[ExpositionFairy Tikal]] makes it TwoGirlsToATeam.
552* SoftReboot: The game served as a "refresh" for the Sonic series after its declining popularity during the [[Platform/SegaSaturn Saturn]] era (in no small part due to the Saturn receiving no mainline Sonic game, only getting [[VideoGame/SonicR spin-offs]] and [[VideoGame/SonicJam ports]]). All of the characters were re-designed to be taller and skinnier (and in Amy's case, older as [[AgeLift she's aged up from eight to twelve years old]]) as opposed to the shorter and rounder designs of the [[Platform/SegaGenesis Genesis]] era, the Japanese continuity was adopted worldwide, with the localization [[CanonDiscontinuity excising old western concepts such as Mobius]] and mainstreaming the name "Dr. Eggman" in the west, the mostly pop-based soundtrack of the Genesis games was replaced by a soundtrack that encompasses multiple genres (though future games would mostly be rock-based), and the games' storylines would become [[DarkerAndEdgier darker and more complex.]]
553* SpaceCompression: Angel Island, normally depicted as a massive, verdant FloatingIsland in the middle of the ocean, appears in the Mystic Ruins Adventure Field as a tiny, almost-featureless island. It appears with its usual size in the CGI cutscenes. From the perspective of the Mystic Ruins explorers, though, it's as if a whole "mountain" suddenly sprang up overnight, and two rather large Action Stages are set on it (Icecap and Red Mountain).
554* SpinAttack: Tails can swipe his tails as an attack, which is upgraded to infinite spinning with the Rhythm Badge. Amy can do the Spin Hammer Attack and swing her hammer while spinning, but she can't move while spinning.
555* SpoilerOpening: The opening cinematic contains the destruction of Station Square and Chaos's final transformation. [[Administrivia/TropesAreTools It may have been intentional, to prevent players from putting the game down after completing Sonic's story.]] Or just to get some extra mileage out of the lengthy FMV sequence.
556* StandardEstablishingSpaceshipShot: The Egg Carrier's various appearances often start with this.
557* StationaryBoss: In Gamma's storyline, E-105 Zeta was turned into a stationary defense unit as punishment for failing to capture Froggy. When Gamma returns to the Egg Carrier after it sinks into the ocean near the end of his storyline, he finds Zeta, who serves as the boss of Hot Shelter. Being a stationary defense unit, Zeta is unable to move from his spot, and instead fires missiles at Gamma. Gamma must destroy Zeta's turrets so that Zeta will malfunction and explode, releasing the peacock trapped inside him.
558* StockVideoGamePuzzle: Quite a few different puzzles appear at varying points across the levels and characters, notably in Lost World.
559* StrikeEpisode: At some point during the stories of Sonic, Tails, Knuckles, Amy, and E-102, the railway workers go on strike, shutting the trains down, and leaving players unable to go from Station Square to the Mystic Ruins, or vice versa. The labor stoppage is eventually resolved.
560* StuffBlowingUp: Sky Deck is full of cannons and explosions. Twinkle Park also features barrels that, once attacked, explode on a timer.
561* SuddenNameChange: The Floating Island suddenly changed to Angel Island as of this game; Angel Island Zone was the name of the first level of ''VideoGame/Sonic3AndKnuckles'', but it wasn't the name of the island itself.
562* SuddenlyVoiced: ''Everyone''. The early games didn't even have ''subtitled lines''. Sonic and Eggman were voiced in old Japan-exclusive arcade games, most famously ''VideoGame/SegaSonicTheHedgehog'', and the former had a few voice clips in ''VideoGame/SonicTheHedgehogCD'' (usually upon getting a OneUp), but not to the extent of this game.
563* SuperPrototype: Subverted with the E-series robots. The first in the line, ZERO (aka E-100 Alpha), is quite inferior to even the 101 model, Beta (and also has a markedly different design compared to every subsequent model). Beta, meanwhile, loses out to the 102 model, Gamma, who then goes on a quest to destroy the rest of the series all the way through 105 Zeta. Beta gets upgraded into a "Mk. II" revision partway through Gamma's story but it doesn't help and it gets destroyed for good in the rematch.
564* TacticalSuicideBoss: There are ''lots'' of them in this game.
565** If Eggman never dug into the ground with the Egg Hornet, there's no way Sonic would be able to damage it.
566** Chaos 2 already has two very effective attacks: one has him bounce all over the arena as a giant ball, and the other covers the entire floor, so why does he have to try to punch Knuckles?
567** Had Chaos 4 never popped out of the water, Sonic, Tails, and Knuckles would have never defeated him.
568** Eggman manages to inflict this on Chaos during the Chaos 6 battle with Sonic or Knuckles. Chaos normally has no vulnerability in his Chaos 6 form, but Eggman insists on hurling ice robots into the arena. Sonic and Knuckles simply throw the ice robots at Chaos when its mouth is open, freezing the beast and making it vulnerable. Had Eggman never gotten involved, Chaos would have been unbeatable.
569** Eggman should know better than to stick his head out of the Egg Viper. He also should know better than to make its wheels separate from its body and move flat-side up.
570* TakingYouWithMe:
571** After the player delivers the final blow to the Egg Viper at the end of Sonic's story, you'll be notified that "he's up to something". Sure enough, Eggman will do a final attack by plowing through the platform Sonic is standing on to drop him. You will need to have at least two platforms left when you reach this stage to survive and win the fight.
572** At the end of Gamma's story, after defeating Beta Mk. II, Beta quickly shoots Gamma before Beta's destruction. This leads to Gamma's own destruction a minute later.
573* TeamRocketWins: Playing Gamma's story at least, which allows you to fight and defeat Sonic in battle (though Amy stops him just short of finishing the job). So far Gamma is the only one of Eggman's robots to individually defeat Sonic in the games storywise (albeit ''[[RashomonStyle branching]]'' storywise).
574* TearingThroughTheMovieScreen: During Amy's Hot Shelter level, you eventually reach a dead-end room with a puzzle for you to solve. The monitors on the walls initially display nothing but static, but once you solve the puzzle, they change to display footage of ZERO angrily shaking its fists at you. A moment later, the real ZERO crashes through the monitors and starts hunting you down; luckily, you can escape through the hole he just created.
575* TechDemoGame: ''Sonic Adventure'' was made partially to demonstrate all the graphical and hardware tricks the Platform/{{Dreamcast}} was capable of. For instance, it's the entire reason why one of the game's antagonists is a being [[MakingASplash made out of water]] -- as an excuse to show off the Dreamcast's state-of-the-art transparency and dynamic morphing effects. The extensive voice acting demonstrates how its games could store vast amounts of CD-quality audio. There were multiple online features like message boards, leaderboards, and DownloadableContent to show off the system's Internet functionality, and even the VMU is given focus with "Chao Adventure".
576* TeethClenchedTeamwork: Knuckles' theme "Unknown from M.E." has a verse which he views teamwork, especially in regards to [[VitriolicBestBuds Sonic]]:
577-->''I have no such things as weak spots'' \
578''Don't approve of him, but gotta trust him'' \
579''This alliance has a purpose'' \
580''This partnership is only temporary... Yeah''
581* TempleOfDoom: Lost World.
582* ThatsNoMoon: The excavation team at the Mystic Ruins is flummoxed by a "mountain" which suddenly appeared from nowhere. Unbeknownst to them (and the player, at first), it's actually Angel Island.
583* ThemeSongPowerUp:
584** Played with in the final battle against [[spoiler:Perfect Chaos]]. "Open Your Heart" (the game's main theme and Super Sonic's personal theme, more or less) plays during the first half of the battle. After you hit the boss a number of times, he revives, and the second half plays out with ''his'' theme. It's subverted because Super Sonic doesn't defeat the boss for good while his own theme is playing, inverted because the villain's own theme is what plays during the second half (after it's rejuvenated) so he's the one powering up to his own theme, and averted because it doesn't do a lick of good anyway (he's already losing by the time its music starts up; you just have to land the finishing blow).
585** Again played with during the Sonic vs. Gamma battle. Depending on who you play as, the character with the upper hand will have their theme play as they get ready to land the final blow, only for Amy to stop them before they can. In Sonic's case, however, it continues so as to be played straight as he heads off to defeat Eggman and Chaos 6.
586* ThisLooksLikeAJobForAquaman: While the other playable characters have cool powers and weapons, Big the Cat has only a fishing pole. While the other characters have exciting, action-packed levels, Big's levels all have [[LivingMacGuffin Froggy]] conveniently end up in some body of water, and the level is spent fishing Froggy out of it (though Big can destroy small {{mooks}} with his fishing pole). It even works this way for Big's {{final|Boss}} (and only) boss. Chaos, the water BlobMonster, absorbs Froggy into its body. To beat the "boss," Big just has to fish Froggy out of Chaos' body. He doesn't really fight Chaos, but the game still treats this as a victory.
587* ThreateningShark: Chaos 4 takes on the form of a shark and is fought in a lake near where Dr. Eggman swiped the Blue and Green Chaos Emeralds from Sonic and Tails. Sonic, Tails, and Knuckles stand atop giant lily pads that Chaos 4 tries to sink in an attempt to drown them. [[TacticalSuicideBoss When Chaos 4 pokes his head out of the water, that's their chance to attack him.]]
588* TimedMission:
589** Tails' stages have him racing against Sonic and, in the last level, Eggman. He has a limited amount of time to get to the goal before they do.
590** All of Gamma's levels and his FinalBoss have a 3 minute timer. The timer can be increased by destroying enemies, with the amount granted being larger if more enemies are destroyed at once. The A-Rank versions of his stages shorten the timer along with requiring the objective be attained with a certain amount of time remaining.
591** All of the A-Rank versions of the stages, with the exception of Big's levels, have a timer. Since Gamma's and Tails' levels are already timed in the other ranks, the time they are given is shortened.
592* TranquilFury: In contrast to his usual LargeHam, Eggman's encounter with Tails in the Egg Walker has him speak this way. Surprisingly, it's very unsettling.
593* TrueFinalBoss: The final story has [[spoiler:Perfect Chaos, who absorbed the negative energy of the Chaos Emeralds]], combatted by Super Sonic.
594* TwoLinesNoWaiting: The game contains six subplots (seven if you count Tikal's) which all come together in the last story.
595* UnbuiltTrope: This game was the first 3D entry in the series and established both a story and gameplay template for the games that followed, but it should be noted that it did some things a little differently compared to those games:
596** This game was notably the first in the series to introduce a LovecraftLite plot where the heroes had to battle an EldritchAbomination, with Chaos being the main antagonist of the game alongside Eggman himself. Unlike the examples that followed him, however, Chaos' desire to cause massive destruction isn't because of [[GenericDoomsdayVillain his inherent nature as a monster]] or even [[ForTheEvulz out of a pure sadistic pleasure]]. Instead, it's revealed that Chaos' wrath is fueled by ''[[TragicMonster grief]]'' for when the Chao he was protecting were brutally hurt by the invading Echidna tribe, and said grief has festered within him to the present day-- where he's first seen being attacked by police officers who shoot him for seemingly no reason other than his monster-like appearance, implicitly confirming to him that [[HumansAreBastards people are still horrible to one another even after thousands of years]]. Likewise, he isn't defeated by being violently attacked to death like the other monsters that followed, but rather [[spoiler:through Super Sonic using the Chaos Emeralds' positive energies to neutralize his anger, allowing him let go of his hate and [[EarnYourHappyEnding have an ultimately happy ending]] like the rest of the cast]].
597** Likewise, this game also had the first major instance of [[BigBad Eggman]] being [[EvilIsNotAToy usurped by a villainous force he intended to control for himself]], its specific case of Chaos usurping Eggman is more complex than those of later games. Chaos spends most of the game perfectly content with working alongside Eggman, and his actions at the end of the game-- reaching his "Perfect" form and destroying Station Square-- were ''technically'' [[TheBadGuyWins what Eggman desired to see happen]], albeit only on his terms. As such, rather than Chaos' betrayal coming from Eggman lacking foresight, Chaos' betrayal is heavily implied to be the result of Eggman betraying ''him'' first, likely through leaving him to die on the falling Egg Carrier. Additionally, Chaos only usurps Eggman's role as the main villain ''after'' all the doctor's other plans have already been foiled by Sonic and Tails, in contrast to how later villains usurped him [[TheStarscream at the earliest opportunity they could find]].
598* UncommonTime:
599** The boss music for Chaos 6 alternates between a 7/8 and a 4/4 time signature.
600** [[https://www.youtube.com/watch?v=6WaLw12XZcY Fanfare 4 "Dr. EGGMAN"]] is in 7/4.
601* {{Understatement}}: Gamma's concise nature of speaking creates such gems as "This is the wrong room" after accidentally walking in on its older "brother" being seemingly cannibalized for parts and upgraded while still active, or "This presents a problem" after being seemingly ''teleported back in time''.
602* UnderwaterRuins: Sonic's section of Lost World has Sonic come across a huge underwater temple with a stone python swimming in it. To escape the temple, Sonic needs to find the three switches that open the exit door, and he must also press switches that raise the water level so that he can ride the stone python to reach the three switches to the exit door. In a later section of the same level, Sonic must light up a darkened temple and avoid falling into the water below it, and when he escapes that, he slides down a water slide leading to the next temple.
603* UnderTheSea: There's watery segments here and there, but the only extended underwater segments are in Big's stages and are mostly optional.
604* UnexpectedGameplayChange: Aside from the other characters' differing gameplay styles, there's the kart-racing section in Twinkle Park (and the related Twinkle Circuit minigame), and the two Sky Chase acts, which are rail shooters where you control the Tornado.
605* UnexpectedShmupLevel: Sonic's story includes the Sky Chase rail shooter levels.
606* TheUnfought: Chaos 1 is never battled, despite being seen in a cutscene. Chaos 3 and 5 are skipped entirely due to it absorbing two Emeralds at once.
607* UnintentionallyUnwinnable:
608** The original release had several glitches that allowed you to get stuck. [[https://www.youtube.com/watch?v=CSmXLrkMlOI You can glitch through the roof of the train station at the beginning of Tails' story, and play through Casinopolis before the casino area was unlocked]]... only to find yourself unable to leave the area, thanks to the pathways to and from Casinopolis still being sealed shut, and stuck there by the game's auto-saving, permanently ruining the entire save file (which has stories for ''six'' characters). It isn't impossible to leave the area, but it requires pin-precision platforming to the point where those with less patience might not find wasting that time to be worth it.
609** You can opt to obtain Sonic's optional upgrade in [[SecretFinalCampaign Super Sonic's story]], which will autosave. If you choose to quit then when you load the game again, you'll get [[NowWhereWasIGoingAgain text indicating what has last happened in the game]], just like in any other character's story. When you obtained the Crystal Ring determines what the text says. (For those who haven't played the game, that's not supposed to happen in Super Sonic's story and it is intended to be played in a single session with no saving -- starting the story begins you at the first cutscene with every run.) When the "previously" text is finished scrolling, the game will freeze. Interestingly, the background art is the CG of [[spoiler:Perfect Chaos]] as he looked ''before'' his final in-game design. Beware that doing this is a death sentence for your save; you will never finish the game if this happens and will need to start over from the very beginning. Later ports have addressed this behavior.
610** In the DX port, if you glitch your way into Twinkle Park with Knuckles and manage to get to the second part of the level, do ''not'' put Knuckles into the bowling ball launchers -- it'll trap him in place and won't let you launch him, forcing you to restart or quit the level.
611* UniqueEnemy:
612** Sonic's version of Ice Cap has badniks that shoot out chilling air that will freeze him solid if he gets too close. They only appear in the first two sections, and do not appear in Tails or Big's version of the level.
613** The first section of Sonic's Twinkle Park has badniks inside go-karts that will attempt to ram into him.
614** Knuckles' version of Casinopolis has the pirate enemies that explode into rings and only appear on the ships in the upper part of the level.
615* UnusuallyUninterestingSight:
616** Tikal and the other Echidna residents seem completely nonchalant about the heroes' presence, or even a ''friggin' robot'' in the flashbacks to the past. About the only reaction they will make is if the player attacks them or jumps on them. Though, it might be because Tikal isn't truly transporting the heroes back in time and rather making them have visions of the past.
617** The explorers in the Mystic Ruins are surprised by the sudden appearance of a "mountain" (actually the crashed Angel Island) within the ruins, but aren't concerned enough to actually explore it, instead focusing their efforts toward the nearby jungle that's been there for centuries.
618* UnwinnableByDesign: A strange decision made in the Reebok challenge DLC. The last signplate of the Reebok challenge is found at the end of the first section of Emerald Coast and it's placed in such a way that will not let you pass by any means. The only way to play the rest of Emerald Coast is to delete the DLC file itself, which it tells you to do when you reach it.
619* UpdatedRerelease:
620** Japan received one in the form of ''Sonic Adventure: International'', which as the title suggests, is a Japanese version of the North American/European release, which patches up several bugs that were present in the original Japanese release.
621** The [=GameCube=] ''DX'' version features redesigned graphics with updated models for the main characters (sans Eggman), added some new features, backported some of ''Sonic Adventure 2: Battle''[='=]s improvements, a catalog of unlockable Game Gear games, and Metal Sonic as an unlockable character for collecting all Emblems. The [=GameCube=] port served as the basis for the PC, Xbox 360 and [=PlayStation=] 3, and Steam re-release versions and features higher resolution graphics with dual-analog controls for the camera, however, the game's ''DX'' content (Mission Mode and Metal Sonic) is sold separately as DLC on the HD console versions (it is thankfully kept in the PC releases) and it's limited to a 4:3 presentation.
622* UpgradeVsPrototypeFight: Gamma the robot is made to fight its "brother" Beta, who is the more advanced of the two. To Eggman's surprise, Gamma wins, so it is charged with carrying out the doctor's missions. Later, Beta is rebuilt and battles Gamma again. Gamma just barely manages to win again, but unlike the previous battle, [[PyrrhicVictory it results in its death]].
623* UtopiaJustifiesTheMeans: Pachacamac's reasoning for wanting to take the Chaos Emeralds; he believes that it will result in prosperity for the Echidna Tribe. It does nothing to cover up his power-hungry nature and lack of regard for others.
624* VacuumMouth: Chaos 6 may attempt to inhale Sonic or Knuckles during the battle against him, but also has the unintended side effect of sucking in any deactivated ice bombs lying around the arena.
625* VideoGame3DLeap: The true first one after the isometric ''VideoGame/Sonic3DFlickiesIsland''.
626* VideoGameCaringPotential: Chao. If you are nice enough to a Chao, it will have a big smile on its face and clap whenever your character picks it up. Beware, however, that being ''too'' nice to a Chao might result in the little guy getting a spoiled personality, making it throw tantrums even when only a little hungry. Balance is the key, but regardless, if the Chao is happy enough, it will reincarnate into a baby at the end of its life.
627* VideoGameCrueltyPotential:
628** Likewise, you can hit the Chao, throw it, put it in water and watch it flail if it doesn't know how to swim, make it starve, and all other sorts of things. Such abuse will result in the Chao crying a fountain of tears, blowing a raspberry at you, or if it's aggressive enough, it'll charge at you and futilely throw punches. If the Chao is more sad/angry than happy, it ''won't'' reincarnate at the end of its life. It was worse in the original version, where you can kill them outright, and E-102 could even ''shoot'' the Chao!
629** To a lesser extent, as you play a stage as Sonic with Tails following you, you will undoubtedly find yourself attacking Tails, either by jumping on him or spin dashing near him.
630* VillainBall: Eggman's programming and distribution of his E-100 series is questionable to say the least:
631** E-102 Gamma's gameplay utilises a timer, with Gamma shutting down if it runs out. The only way to replenish it is to shoot enough targets. Of course Eggman has also sent out an army of badniks per area, leaving them Gamma's primary method of keeping his timer going.
632** After Gamma proves more competent than his brethren, Eggman fires the other three E-100 models off the elite squad to do other random less important duties. This leaves Gamma to fight Sonic solo shortly afterwards. Given Gamma alone is implied to be a tough opponent for Sonic (almost killing him in Gamma's own storyline), things might have gone quite different if Eggman had kept his other three E-Series.
633* VillainousBreakdown: An absolutely chilling one from Eggman at the end of Tails' story, not shown anywhere else. Due to the loss of both Chaos and the Egg Carrier, Eggman '''snaps''' and completely ditches his LargeHam and CardCarryingVillain tendencies and goes from a cackling, somewhat intimidating MadScientist to an OmnicidalManiac with a horrifyingly low growl of a voice. He then attempts to ''nuke Station Square with himself in it'', and very nearly gets away with it if not for the missile being a dud. After Tails beats him to the missile and disarms it, Eggman snaps ''further'', jumps in a giant spider-mech and resolves to kill everyone himself. This line absolutely seals it:
634--> '''Eggman''': (in a low growl, directed at Tails) You '''fool'''. Away! Before I make ''mincemeat out of you.''
635* TheVoiceless: Chaos never says a word outside of bubbles and ripples in the altar pond during the flashbacks, and Tikal is the one who relays his feelings to others.
636* WarmUpBoss:
637** For Sonic, Chaos 0, a brief and easy boss fight that the entire game starts off on.
638** For Gamma, he first fights E-101 Beta, a boss [[ZeroEffortBoss so incredibly easy]] that it can be beaten in less than ''five seconds'' by just button mashing Gamma's cannon.
639* WaterfrontBossBattle: Chaos 4 is fought in the pond near the entrance to the jungle. Sonic, Tails, and Knuckles have to stand on [[LilyPadPlatform giant lily pads]] while Chaos 4 swims in the pond, and attack his head when he pokes it out of the water. Because it can sometimes take a while for him to poke his head out, he can on occasion be one of the longest boss fights in the game.
640* WelcomeToCorneria: [[AvertedTrope Averted]]. The [[NonPlayerCharacter human citizens]] of Station Square and the Mystic Ruins have different conversations depending on who they're talking to and storyline progress. There's even a few subplots, such as a [[ShrinkingViolet shy girl]] steadily gathering the courage to ask a burger shop employee out, a disgruntled railroad employee eventually [[StrikeEpisode starting a labor strike]] ([[BrokenBridge temporarily blocking access to the Mystic Ruins]]), and a couple breaking up over an affair.
641* WhamEpisode: Besides being the series comeback into the mainstream, it shook a lot of things up in terms of content. The threat of Eggman is usurped by a monstrous, magical deity. The Chaos Emeralds are upgraded from bonus power-ups to magical, plot relevant artifacts, and their backstory is finally shown and elaborated upon. The tone is darker and the stakes are raised much higher than previous threats in the series. This was also the first game in the franchise where a character (or rather, an entire civilization) was out-and-out killed.
642* WhamLine: Spoken just before Gamma's final boss fight by Gamma himself, making it clear that his story will ''not'' [[BittersweetEnding have a happy ending]].
643-->"Units remaining... Gamma... Beta..."
644* WhatYouAreInTheDark: Despite having the ability to simply walk away from the conflict between Eggman and the heroes, Gamma opts to go on a mission to free all of the Flickies captured in the E-100 robots, even though this will also end in his own demise.
645* WheelOFeet: Sonic when running at top speed, but only in the original Japanese release of the game. The International version and all future versions removed the effect.
646* WheresTheKaboom: Towards the end of Tails' story, Eggman, having lost Chaos and the Egg Carrier, decides to destroy Station Square by blowing it up with a missile. But to his dismay, it fails to explode. He goes to detonate the warhead, but Tails beats him and disables it.
647* WoobieDestroyerOfWorlds: Chaos. [[spoiler:He only acts antagonistically because he has been sealed away so long without proper closure to the attack on the Chao and the emerald altar]].
648* WordSaladLyrics: Knuckles and Big's themes have their moments, but special mention goes to Amy's theme, "My Sweet Passion":
649-->I do understand the feelings of a Persian cat\
650(But the Sphinx looked so cute I had to shave it)\
651He reminds me of parsley when he's standing there all alone\
652(Makes me wanna be his speciality)
653* YeahShot: All the characters' end of act poses. Sonic and Tails' endings do one as a CallBack to those of the classic Genesis games.
654* YouHaveFailedMe:
655** Eggman sorta does this to Gamma's E-Series brethren after they fail to retrieve the Chaos-enhanced Froggy, dispatching E105ζ (Zeta) for a torturous upgrade and demoting E103δ (Delta) and E104ε (Epsilon) to random areas.
656** After Sonic, Big, and Knuckles foil their VillainTeamUp one last time and Eggman leaves him for dead on the sinking Egg Carrier, Chaos attacks the doctor out of spite before going solo. An angry Eggman later attempts revenge with the Egg Carrier 2, but Chaos, now in Perfect form, quickly swats him away again.
657* YourSizeMayVary: Similarly to when they are upgraded to the Super Emeralds in ''Videogame/Sonic3AndKnuckles'', the Chaos Emeralds are shown to be much larger at the Master Emerald shrine [[https://imgur.com/WysLzdI in the past]] than in the present day.
658* YoYoPlotPoint: The narrative arc of Big's story--each level consists of Big trying to catch Froggy and succeeding, only for the events that follow causing him to lose Froggy once again. After the Emerald Coast level, for example, Big only has Froggy for a scant few seconds before Gamma yoinks the frog away (there's even a little bell that rings, the instant of the theft).
659* ZeroEffortBoss: The first fight against E-101 Beta in Gamma's story can be beaten in less than ''five seconds'' without even getting a chance to fire a shot by just button-mashing Gamma's cannon.
660[[/folder]]
661----
662->''The servers are the seven Chaos.\
663Chaos is power; power enriched by the heart.\
664The controller is the one that unifies the Chaos.''

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