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[[quoteright:350:[[VideoGame/SonicAdventure http://static.tvtropes.org/pmwiki/pub/images/perfect_chaos.jpg]]]]
[[caption-width-right:350: [[EldritchAbomination Yet this game somehow got an E rating.]]]]

No, not even [[Franchise/SonicTheHedgehog the Blue Blur]] can be trusted not to [[NightmareFuel give kids nightmares]].

!!These entries have their own pages:
* NightmareFuel/SonicTheHedgehogCD
* NightmareFuel/SonicShuffle
* NightmareFuel/SonicAdventure2
* NightmareFuel/ShadowTheHedgehog
* NightmareFuel/SonicTheHedgehog2006
* NightmareFuel/SonicLostWorld
* NightmareFuel/SonicForces
* NightmareFuel/AdventuresOfSonicTheHedgehog
* NightmareFuel/SonicSatAM
* NightmareFuel/SonicUnderground
* NightmareFuel/SonicX
* NightmareFuel/ArchieComicsSonicTheHedgehog
!!Other entries:

[[folder: General]]
* [[http://www.youtube.com/watch?v=9Yw5jkAHgME The infamous drowning theme]] frequently reduces (most) players to tears while playing through Labyrinth Zone in ''VideoGame/SonicTheHedgehog'', if only because of how [[JumpScare louder-in-comparison and unexpected]] it is. The ''VideoGame/SonicAdventure'' [[VideoGame/SonicAdventure2 games]] [[http://www.youtube.com/watch?v=IBpWn0j8A-0 feature an orchestrated version of it,]] [[http://www.youtube.com/watch?v=Eeub2_fm_Qc complete with realistic drowning;]] and, last but not least, ''VideoGame/SonicColors'' has an even more ominous-sounding, better-orchestrated version of the track, [[http://www.youtube.com/watch?v=HMUOMZNEzXw as heard here.]] What makes drowning in ''Colors'' even scarier is [[http://www.youtube.com/watch?v=COPybKtOceQ Sonic's body language]] during it, depicting an even more realistic drowning. However, [[http://www.youtube.com/watch?v=Fg0t9eK3jg4 arguably the worst]] version is the ''VideoGame/SonicGenerations'' one, which combines the fast tone of the regular version with incoherent drumming.
** At a game show called Banzai Arcade's panel at an anime convention, one of the backdrops to one of the [[NintendoHard hard]] questions was a [[SugarWiki/AwesomeMusic "Labyrinth Zone]] [[http://www.youtube.com/watch?v=H7ibpUL7Qv8 Dance Party"]]. Missing the question leads to the water level rising drastically, with [[https://youtu.be/q6GfLhut0dg?t=4m54s predictable results]].
** Tails lampshades this in ''VideoGame/SonicGenerations'' by saying the water in Chemical Plant Zone makes him really nervous.
** The drowning music also plays in some games at 9'49" out of [[TimedMission 10 minutes]]. Most levels are short enough that this doesn't happen, but ''Sonic 3 & Knuckles'' and ''Sonic Mania'' have substantially long enough levels that it's likely to happen, especially in Carnival Night Zone Act 2 (thanks to the [[ThatOnePuzzle notorious red barrel]]), both Acts of Sandopolis Zone, and ''Mania''[='=]s Flying Battery Zone Act 2.
* Sonic's DeathThrows sprites can easily catch the player by surprise, especially if it happens while traveling at high speeds -- the sudden stop is almost like a JumpScare of sorts.
* Death by getting crushed is one of the most common and feared ways of dying after drowning, due to the fact that ''nothing'' protects against it. You can be Super Sonic with 300 Rings remaining and still be paranoid around platforming sections because something could unexpectly come down upon you or a moving platform you're on could push you up into the ceiling or a bed of upside-down spikes.
** Oddly enough, ''Sonic Generations'' severly downplays this; yes, you can get crushed, but it's not a OneHitKill -- if you have rings, they'll fly out of you as usual as Sonic is comically SquashedFlat, springing back into shape several seconds later.
* The [[AndIMustScream And I Must Screamness]] of the games, concerning the woodland animals' UnwillingRoboticisation.
* Robotnik's classic western design. Once an [[http://eggmanempire.sonicworld.net/downloads/images/official/classic/poses2.gif adorable]] [[http://eggmanempire.sonicworld.net/downloads/images/official/classic/poses.gif spherical humanoid]] with traits of [[Music/TheBeatles both eggs and walruses]], his cutesy appearance was changed [[AmericanKirbyIsHardcore when he hit American and European shores]], and he was molded into this [[http://eggmanempire.sonicworld.net/downloads/images/official/soa/chaosartwork.png much more]] [[http://eggmanempire.sonicworld.net/downloads/images/official/soa/Spinball_eggman.png menacing creature.]]
* Sonic's eyes, as well as those of a few buddies of his, look a bit too much like a single eyeball with two pupils.
** [[http://sonicintent.blogspot.com/2009/06/sonicnot-so-universe-rant-warning-ahead.html The .gif at the end of this blog post]] makes this [[BodyHorror all too clear.]] [[spoiler:It's a picture of Sonic, with the "bridge" between his eyes ''lifting up'' and his pupils '''''becoming one.''''']]
** It was ''much'' worse in [=DiC=]'s Sonic cartoons, [[http://imageshack.us/photo/my-images/696/shot1cm.png particularly SatAM]]. And as if his eyes weren't already freaky enough, for some bizarre reason Sonic didn't have eyelids, [[http://imageshack.us/photo/my-images/5/noeyelids.png/ so he was unable to close his eyes or squint]]. [[{{Squick}} Squick!]] [[http://imageshack.us/photo/my-images/715/shot2r.png/ This is what the animators depicted him like when they wanted to make it look like he was "closing" his eyes...]]
* A lot of Tails's backstory can be considered this. [[AdultFear He has no known family in the game continuity and was constantly bullied in most adaptations. Even after that, Tails was constantly kidnapped, threatened as well as nearly getting killed]] by Robotnik, [[VideoGame/SonicTheHedgehog2 twi]][[VideoGame/SonicAdventure ce]].
* Metal Sonic, not just because of his [[Main/RedEyesTakeWarning intimidating]] [[UnnecessarilyCreepyRobot design]] and [[KillerRobot modus]] [[ThereCanOnlyBeOne operandi]] but also because he barely toes the line between your average EvilKnockoff RobotMe and a full-on MechanicalAbomination at times. Reaches its absolute peak in ''[[VideoGame/KnucklesChaotix Knuckles Chaotix]]'' and ''[[VideoGame/SonicHeroes Heroes]]'' when he transforms into Titan Metal Sonic and his gradual transformation into Metal Overlord respectively.
* In games where the FinalBoss must be fought with Super Sonic or Hyper Sonic, there is usually a pretty terrifying consequence if Sonic runs out of rings. For example, Sonic falls into the Earth's atmosphere, implying that he dies [[ReentryScare of reentry burnup]] or [[NotTheFallThatKillsYou by falling a loooooooooong way down]] in ''Sonic 3 & Knuckles'' and ''Sonic Adventure 2'', and in ''Sonic Adventure'' he falls into what appears to be tens of meters of water and drowns.
* The [[BattleshipRaid "raiding a massive air fortress"]] stages such as Wing Fortress Zone and Flying Battery Zone are frequently set high in the sky, and have some sections where you're platforming along the underside of whatever you're on. Sometimes the game is merciful enough to trigger death by BottomlessPit right away if you fall without scrolling further. However, sometimes the game will scroll down a few screens before you finally hit the kill line, just to reinforce how high you are above the planet surface and set off acrophobia.

[[folder: Sonic The Hedgehog 2]]
* In the 2-player vs. mode, when one player finishes a level, it starts a 60-second countdown for the other player to try and finish. The drowning music is once again involved (see folder above).
* The Chemical Plant Zone is mostly remembered because of the quickly rising purple water with no air bubbles known only as Mega Mack, making any comeback to the surface more and more difficult as time went by, eventually culminating in an inevitable instance of the drowning countdown. This is referenced in VideoGame/SonicGenerations, where Tails remarks about how [[FandomNod "and that pink water really makes me nervous for some reason."]] drives home how even Creator/{{Sega}} is aware of the level's infamy.
* Aquatic Ruin Zone features stone with Robotnik's face carved on it, randomly activating arrow traps, and of course, [[RunningGag water for Sonic to drown in.]]
* The teleportation boxes freaked out some people as well, what with the music and the whole screen turning white [[http://www.youtube.com/watch?v=sNi78G9IigU#t=1m10s as seen here.]]
* In the Genesis games 2 and 3/Knuckles, there's a few [[SuicideAttack kamikaze]] [[TakingYouWithMe enemies]] (Asteron in Metropolis, Jawz in Hydrocity).
* Mystic Cave Zone has a particular part in which the player must grab a vine or else drop into an inescapable pit of spikes, able to trap even Super Sonic.
** Thankfully, the 2013 mobile re-release of the game turned it from a death trap into a WarpZone to Hidden Palace Zone.
* Playing around with savestates on this game and [[ROMHack Sonic 2 Retro Remix]] with an emulator [[http://www.youtube.com/watch?v=tKD1303YiJI can result in a messy outcome.]]
* The infamous Sonic 2 prototype has the infamous blank stages: Wood Zone Act 2, both acts of Cyber City Zone, and both acts of Death Egg Zone. No level, just glitched (if any) background) and plummeting to your death three times. Even worse, playing Death Egg Zone, which has [[NothingIsScarier no music]], ''shuts off the [=Z80=] processor'', preventing sound from playing again until you reset.
* Oil Ocean Zone's music is a bit creepy. What elevates it into Nightmare Fuel territory is that if you input a code on the wrong menu (entering 1-9-9-2-1-1-2-4 into the Options sound test rather than the stage select sound test), which not only give the player 14 continues, the music starts playing throughout the entire game, even if you navigate outside of the options menu. Worse, all sound effects are disabled!

[[folder: Sonic Spinball]]
* "Pinball Fortress" may sound cheesy. [[http://www.youtube.com/watch?v=7rs3xC6Cxmk&#t=0m20s It isn't.]]
* Unlike milder Badniks, [[http://info.sonicretro.org/Rexxon Rexxon tries to eat Sonic whole...]]
* In [[http://www.youtube.com/watch?v=SqR23N_2AQA#t=1m25s this level,]] the music is disturbing enough, but the painful screech sound Scorpius makes is way too fitting.
* The boss of Lava Powerhouse, Roboboiler, is this because of its appearance: [[http://www.youtube.com/watch?v=Paq4kdpZumY&#t=2m00s Four disembodied Robotnik heads that vomit magma every time they're hit.]]
** Fall down the drain during that boss battle, and Sonic falls to an area where he is hanging mere feet from a lava cauldron by a chain.
* [[http://www.youtube.com/watch?v=i8nDfAW4EKg&#t=4m32s The fully-functional Roboticiser with eyes.]]
* Fall down an outlane and you get the ScareChord and a HaveANiceDeath message in red text.
--> '''READY TO FRY?''' TOO BAAAD...
* The GameOver music is [[http://www.youtube.com/watch?v=mqPy9GR4Ekw pretty]] JumpScare-inducing. You can easily put it to these lyrics: "OH MY GOD OH MY GOD OH MY GOD OH MY GOD NO NO NO NO NO NO NO NO..."
* Sonic's DeathThrows are a lot creepier, with Sonic even letting out a distorted scream as he flies off the screen.
* The [[https://www.youtube.com/watch?v=unhrHJWueeg 256 glitch levels]] that can be accessed through hacking are all sorts of nightmare fuel. WARNING: SensoryAbuse.

[[folder: Sonic The Hedgehog 3 & Knuckles]]
* To start, a very large portion of Hydrocity Zone is underwater, with all the series-traditional scares that go with it. Then Act 2 comes and it starts with an AdvancingWallOfDoom with very loud rumbling noises.
* Sandopolis Zone's Act 2, set inside a huge pyramid with a scarier version of Act 1's theme playing in the background. About a quarter of the way through, you'll land on a capsule that dispenses a crowd of ever-growing ghosts.
** It's even worse when you're playing as Knuckles in that part of the act: Giving his story takes place after Sonic's one, the ghosts are in the red zone already, and ambush you as soon as the act starts, without rings.
* Ice Cap Zone has a (normally) Knuckles-only section where you must glide from wall to wall while avoiding icy spiked balls. Hacking confirms said spike balls can hurt Super Sonic as well.
* While [[http://www.youtube.com/watch?v=gHwHiymSojk the music]] for Carnival Night Zone sounds awesome, the stage the song plays in is not only ThatOneLevel due to [[GuideDangIt the infamous red-and-white barrel section]], but the sudden stop of all sound whenever the snares pop up can be unsettling.
* The scene where Knuckles gets [[XRaySparks electrocuted]] when he tries to retrieve the Master Emerald can be scary to a few. Not to mention the device is plugged into his ears. That's gotta fucking hurt.
* The Big Arms, when fought in standalone Sonic the Hedgehog 3, its grab attack is capable of ''knocking the rings out of Super Sonic.'' It's a shock to those used to the idea that Super Sonic is invincible to anything that isn't getting squished, a BottomlessPit, or the [[TimedMission time limit]].
* In the Doomsday Zone, [[SongsInTheKeyOfPanic if Super or Hyper Sonic's ring count drops to 10 or less, the already-frantic music will accelerate]]. If he runs out of rings, he falls out of orbit, and we can very much assume that he fell hundreds of kilometers and [[ReentryScare died of reentry burnup]] or the world's biggest freefall.

[[folder: Sonic R]]
* The Tails Doll. Even though fans "made him creepy," an UncannyValley CreepyDoll based off Tails that has a '''''''BLOOD-RED''''''' gem dangling over his head is rather creepy enough already.

[[folder: Sonic Adventure]]
* There are very few places in this game where you can drown without doing so on ''purpose''. Accessible water that goes over the characters' heads is relatively scarce, and the water you do find that meets this criterion can usually be escaped with a single jump. However, if you ''do'' find yourself in a tight underwater situation (usually with Big the Cat), all your childhood nightmares will come to life as the infamous drowning music from the Genesis games plays, this time embellished with an ''entire orchestra''.
* Red Mountain, a [[Franchise/{{Metroid}} Norfair]]-like U-rated hell, with the addition of walls with cells containing ghosts dressed in prison uniforms and scary spiders. A mission card in ''Director's Cut'' hits the SurpriseCreepy home:
--> '''Mission:''' [[BlindIdiotTranslation A fugitive have escaped from the jail of burning hell!]] Find the fugitive!
* Perfect Chaos, [[http://www.youtube.com/watch?v=_efv7ZGAdjo as seen in the intro to the game.]] A gigantic snake-like beast made of water materializing out of a building.
* The Lost World has creepy music, a spooky underground city, and dark areas. Kinda unsettling. And at the end, [[http://img1.wikia.nocookie.net/__cb20120522221349/sonic/images/3/3b/SA1_PerfChaosMural.png a mural of Perfect Chaos destroying Knuckles' entire tribe]]; Sonic, not knowing what it is, is flummoxed.
** Falling off the snake can be traumatizing; as Sonic raises the water level, it eventually becomes impossible to make his way back up, leaving him to either drown or jump off into the endless abyss. And the snake is glitchy; it's all too possible to simply fall right through it as it's moving.
* The flashbacks to the past that Tikal takes all of the playable characters on reveal the dark backstory to the reason Chaos exists, and why Knuckles is the last of his tribe. In his tribe, a girl named Tikal befriends the Chao. Her militaristic father, Pachamac, wants to take the Chaos Emeralds for himself and has no problems with slaughtering all of the Chao along the way; he doesn't even hesistate to throw back his own daughter. This [[PapaWolf naturally]] triggers Chaos' BerserkButton and he destroys the entire tribe, and to stop him from destroying the entire world, Tikal has to ''seal Chaos and her own soul inside the Master Emerald''.
* Eggman's [[http://www.youtube.com/watch?v=ACbOLM17LlU&t=15s "You fool. Away, before I make mincemeat out of you..."]] line. It's supported by the exhausted way in which he realizes that Tails beat him to the missile, and then he threatens to make them all pay for this before he summons the Egg Walker -- this is one of those few times the Eggman makes a genuinely threatening line.
* Amy's entire story, involving her being endlessly chased by a persistent robot called ZERO. It ''never'' stops following her. The worst part is that certain times, [[NothingIsScarier ZERO seems to disappear, only to crash through a wall and continue chasing you]]. As Tikal puts it in her calm, emotionless voice, ''"The robot that was following you is closing in on you. It'll be over if that robot catches you."''
** Amy's Twinkle Park. It starts out just fine, outside in Pleasure Castle's amusement park with the cheerful ride music playing. Then, unlike any other character who visits the level, Amy unlocks the castle's main doors and gets to go inside. [[https://www.youtube.com/watch?v=uO1PRGcZNXY It quickly becomes clear that something is very wrong with the rooms inside.]] And the best part? ZERO. Still following you.
** In Hot Shelter, one part involves Amy collecting colored cubes to fit in slots that will supposedly do something. The area has video monitors all around it that all display static. Once the last cube is placed, the screens go silent, then cut to shots of ZERO threatening you... cue the real ZERO ''smashing through the screens'' and blasting you. You escape the room through the hole it made.
* The Limestone cave level [[http://www.youtube.com/watch?v=ypTdjSrZB6Y has yet another example of spooky music.]] The area itself inspires some acrophobia, especially as slipping just a little off the precarious ledges can send Sonic plummeting all the way to the bottom.
* One NPC in the Mystic Ruins implies that his friend never found a way out of the maze-like jungle.
* The Continue music, aptly called "Will You Continue?". It's like you're in a between-life-and-death limbo.
* The depictation of Station Square after Perfect Chaos goes on a rampage in the Final Story is legitimately horrifying [[AdultFear in a real sense]], and is may even remind you of recent tsunamis and floods in various places, [[HarsherInHindsight like New Orleans, New Jersey, and Tokyo]].
** Perfect Chaos first appears by bursting out of a skyscraper. [[HarsherInHindsight Fast forward to September 2001 in New York.]]

[[folder: Sonic Heroes]]
* [[http://www.youtube.com/watch?v=YB25ZDKsaVg Final Fortress]] is perhaps Eggman's most massive AirborneAircraftCarrier to date, and when you're in the level, you're surrounded on both sides by dark mechanical corridors, flashing lights (which do not light up the place), metal conduits, and caution markings. All of this happens thousands of feet in the air, in the middle of rough weather. [[http://www.youtube.com/watch?v=tB1Z338gcsU The music]] is quite possibly the most mournful, ominous, and heavy piece of music [[WhatDoYouMeanItsForKids ever made for a kids' game]].
* Neo Metal Sonic's transformation into [[OneWingedAngel Metal Madness]] [[http://www.youtube.com/watch?v=FaCFMFOGR6Y in Last Story]], and his scene in the cutscene before Sonic goes Super Sonic, can both be scary to younger audiences: perhaps as a form of AudienceSurrogate to that, the six-year-old Cream is shown during the scene being hugged by Big due to how terrifying it is to her (probably doubles as a mini CrowningMomentOfHeartwarming).
** Even Eggman's army of Egg Pawns and Metal Sonic's army is fleeing the scene in sheer terror when Metal Madness appears.
-->'''Neo Metal Sonic''': ''[[http://www.youtube.com/watch?v=G1w1Qcn9fqU All living things kneel before your master!]]''
** [[WhamLine "All life form data...]] [[http://www.youtube.com/watch?v=UycPI4jEhvY successfully copied."]]
* Egg Emperor, Eggman's ImplacableMan of a final mecha. The BossBattle takes place on the aforementioned Final Fortress.
* The last leg of Lost Jungle. It starts with a group of black frogs, which summon rain that kills plants, trying to drown you in the swamp by making the platforms beneath your feet disappear. Then, when you get away from them, a '''giant alligator''' bursts out of the swamp and starts chasing you. The rest of the level is a mad dash towards the finish line across a series of vine swings, with the alligator snapping at your heels all the way, where one mistake will likely mean instant death.
* Arguably, the ghosts in Hang Castle/Mystic Mansion. They appear out of nowhere, have a creepy laugh, simply fade when hit (just before reappearing in a couple of seconds), and even the characters admit that they make absolutely no sense. And as if that wasn't bad enough, imagine dropping into a room swarming with them, with walls that appear to be made of TV static. And in case you were going to get vindictive and try to Chaos Inferno all of them... they're immune to Team Blasts. Have fun.
** Also, in the Super Hard Mode version of Hang Castle, they will appear in much bigger sizes. Particularly, if you go to a small room, you will notice a giant laughing pumpkin head is appearing right in front of you, filling up the entire room.
** [[EldritchLocation Mystic Mansion]] in general. With switches that make statues and paintings come to life and attack, hallways that never end until you find the way out, doors leading into ''nothing'' and the aforementioned TV static room, the entire place is one massive MindScrew.

[[folder: Sonic Advance series]]
* ''Sonic Advance 2''[='=]s ThatOneBoss is the Egg Saucer, that can deliver [[OneHitKill insta-kill slap attack]] at will, and is piloted by a manipulated Knuckles (if playing as Sonic for the first time), although the special battle theme [[LongSongShortScene used only for Knuckles]] may be either a bit creepy or [[CrowningMusicOfAwesome just plain awesome.]]
* The first ''Sonic Advance'' uses a fairly pleasant -- and unused anywhere else in the game -- sprite depicting Eggman's "pointing" artwork as an after-credits message, as a [[TheStinger stinger]], telling the player "Hey, go collect all the Chaos Emeralds!"... with a pitch black background. The message in the second ''Advance'' game, on the other hand, has a slightly modified version of the Eggman "menacing-and-greedy" sprite from the ''Sonic Advance 1'' intro, still with a black background, telling the player to collect the Chaos Emeralds, but this time in all caps with a ScareChord thrown in for good measure. The image itself can be [[http://www.vgmuseum.com/end/gba/b/son2son.htm seen at the bottom of this page.]]
** It doesn't help that collecting any of the Chaos Emeralds, especially the last two, is absurdly difficult. The Special Stages in this game are thoroughly NintendoHard.
* ''Sonic Advance 2'' is one of the only games in the series to pose the question "what happens when Dr. Eggman's space stations are destroyed?" Well, it turns out that they descend to Earth and destroy whatever area they land in a giant explosion.

[[folder: Sonic Riders]]
* ''Sonic Riders'' is a game you'd think has absolutely no potential for nightmare fuel whatsoever... until you race in the Digital Dimension track, the first half of which is a hellish landscape with creepy gargoyle statues and skeleton hands that try to drag you into a pit. Its potential for inducing nightmares is lampshaded in mission briefings as Storm the Albatross says he's scared of the place. The second half of the track is FluffyCloudHeaven. Sounds like a relief, but it comes across more as unnerving.
* In the game, all characters can attack each other. These attacks change as the racers collect rings and level up. Most of the attacks are quite cartoonish and comical, but Sonic's Level 3 attack happens to be spinning into another racer and repeatedly and brutally smashing them into the ground as Sonic spins, while the sound of ''bones cracking'' is heard.
** Those who aren't bothered by said attack, well, they've probably crashed into walls so many times they're pretty sure they're just hearing the usual collision sound.

[[folder: Sonic Unleashed]]
* Dark Gaia, when it goes OneWingedAngel, transforms [[TransformationTrauma in a really disturbing manner]], and the final product is somewhere between StarfishAlien and EldritchAbomination. Its head is a Venus flytrap filled with eyes, the whole thing enclosed in tongues with two huge ones hanging down.
** And when Sonic attacks Dark Gaia's eye, [[{{Squick}} causing it to leak green blood]]... this is also the reason why the game received an ESRB rating of E10+.
* In the opening, Eggman actually manages to split the Earth apart into seven pieces (akin to ''Sonic Advance 3'').
** And the way that we see ''Super Sonic'' struggling and getting forcibly de-powered by being electrocuted and having the Chaos Emeralds ripped from his body then drained. What really makes the scene disturbing is how Sonic is screaming in agony as this happens.

[[folder: Sonic Colors]]
* The closest Eggman has gotten to a true MoralEventHorizon in the games: He tried to capture an entire alien species, the Wisps, just so he can use their life energy to power his machines, which could've brought the Wisps to extinction if Sonic and Tails failed to stop him. Eggman's master plan was to use them to power a mind-control weapon that's powerful enough to enslave the entire universe.
** To give you an idea of how much of a MoralEventHorizon this is, note the similarities to Black Doom's plan in ''VideoGame/ShadowTheHedgehog''.
* From the Wii version, the [[http://www.youtube.com/watch?v=_U-kliMM3lg Sonic Simulator theme,]] which in the DS version is orchestrated.
** It actually makes sense, as it's actually an 8-bit version of [[{{Leitmotif}} Eggman's theme]] from Sonic '06. So it's a villain theme, and a very [[http://www.youtube.com/watch?v=h7QHG3YmC3s menacing sounding one at that]].
* Run out of Drill power while still underground and [[BuriedAlive you die]]. It's the ONLY wisp that can kill you if it runs out. Thankfully not the case if you're using Drill underwater, but then again, [[OxygenMeter it's]] water.
** Worse yet is that you can save yourself from drowning by using a drill, but when the drill runs out, [[HereWeGoAgain it does NOT reset your air beyond restarting the countdown.]] You'll typically run through an air bubble or two while in a drill, [[OhCrap but when you don't...]]
** The sudden robots that come out of nowhere while you're underground can come off as a shock.
* Purple and Violet Wisps. They were once normal Wisps that were captured by Eggman and forced to obey him, and as such were turned into [[http://images.wikia.com/sonic/images/e/ee/Sonic_Colors_-_Purple_Wisp_511_x_599.png this]] and [[http://images.wikia.com/sonic/images/b/bb/Wisp_Violet.png this]].

[[folder: Sonic Generations]]
* The Time Eater kidnapping Eggman after the Death Egg Robot boss fight. Hearing Eggman begging Sonic to save him doesn't help at all.
* The appearance of the [[EldritchAbomination Time Eater]]. We find out that [[spoiler:it's actually an [[EldritchAbomination Eldritch]] [[TimeMachine Time-Destroying Mecha]] found and utilized by Dr. Eggman of the future right after his recent defeat from ''Sonic Colors'']]. Even worse, when Eggman explains how he found the Time Eater, [[spoiler:the player is shown gray scale images that show the rotund scientist discovering said monster in deep space with Orbot and Cubot, as his is their fate at the end of ''Sonic Colors'']]. However, once Eggman sees the Time Eater, he goes after it on his own, [[spoiler:leaving Orbot and Cubot in deep space forever]].
** Despite this, the robot duo somehow manages to return to the Earth.
* The gate to the FinalBoss fight with the Time Eater looks huge and daunting, [[NothingIsScarier the music stops when you're around it, and until you insert all seven Emeralds, it's completely silent]].
* The implications that Sonic's friends may actually be self-aware while petrified: According to Tails, when he was petrified, [[AndIMustScream he felt like he was helplessly floating in a limbo without a body.]] Tails even says he's going to have nightmares from it, and we can't blame him.
** If that doesn't convince you, also consider Cream's [[https://youtu.be/wzGkcv8TcuI?t=72 line]] if you complete Speed Highway with Modern Sonic.
* The newly-designed [[VideoGame/SonicAdventure2 GUN military truck.]] After exploring the high-def redesign of City Escape, a player who hasn't seen previews would expect the truck to simply drive down a hill at reasonable speed like the original, [[spoiler:but now it's much bigger, it's even faster, and it's been equipped with three gigantic saw blades and rocket boosters, with the worst regard to human safety, as it proceeds to smash through a building quickly. As for all those cars that were just knocked about, they explode upon touch.]]
** It's also pretty frightening during the Classic Stages. It skirts the line of the SlidingScaleOfComedyAndHorror, where its sporadic slamming into walls, crashing into you and anything else around you, actually smashing and [[SquashedFlat flattening]] you against the wall if you aren't careful, and trying to drive into a wall while you're not even there is either terrifying or hilarious.
* [[http://forums.sega.com/showthread.php?432434-Sonic-Hasn-t-Been-Darker&p=7713957#post7713957 This fan theory]] involving Eggman's plan in the game. [[spoiler:Made even worse in that ''VideoGame/SonicForces'' shows it to be '''''absolutely correct'''''.]]

[[folder: Sonic Mania]]
* The trash heaps in [[VideoGame/Sonic3AndKnuckles Flying Battery Zone]], containing pieces of busted-up badniks. It's quite unnerving to see familiar enemies missing eyes, limbs, or even ''their entire face''.
* Stardust Speedway Zone Act 1 has the seed capsules from ''Sonic CD'' that mark the end of a Round in ''CD'' and release seeds that sprout into flowers. That's not too bad. Then a vine grows out of it, with leaves that can be stepped onto and ''{{Man Eating Plant}}s'' branching off of it.
* Hydrocity Zone Act 1's boss. You're ''chopping Eggman up with a propellor''. Granted, he tried to do exactly that to Sonic, Tails, and Knuckles back in ''Sonic 3 & Knuckles'', but still, thank God the game doesn't take itself too seriously.
* Hydrocity Zone Act 2's boss is entirely an UnderwaterBossBattle, and the only way to get air bubbles as you speed through the corridors is to touch the bombs and have them go off in Eggman's face. Missing too many bubbles or bombs is a one-way ticket to drown-town.
* If you have a Flame Shield active in Oil Ocean Zone and you hit an oil slide, pool, or the titular sea itself, or one of the fire enemeis shoots its fire into the oil, the oil will ''ignite'' in a terrifying display of pyrotechnics, and yes, it will hurt you if you don't have a Flame Shield active. And then there's Act 2: The oil in the rigs start emitting toxic fumes around the zone that get thicker and eventually [[InterfaceScrew clouding it]] and draining Sonic's rings once it's thick enough. Sonic has to find switches to clear the fumes for a short while. Small wonder, since this is based off Sandopolis Zone Act 2, one of ''VideoGame/Sonic3AndKnuckles''[='=] biggest sources of NightmareFuel, with the music having similar undertones to boot. Finally, [[ThatOneBoss the boss]] is a submarine shaped like a giant Octus badnik.
* The final zone, Titanic Monarch Zone, has menacing background music and "HBH" banners with Eggman's likeness on them that make you feel like you're running through ''Nazi Germany''.

[[folder: Other Games]]
* ''[[VideoGame/SegaSuperstars Sonic & Sega All-Stars Racing]]'' has the haunted mansion racetracks: the scariness, here, is a given, considering they come from ''VideoGame/HouseOfTheDead''.
** In ''All-Stars Racing Transformed'', the XRaySparks that are the result of being electrocuted reveal that the characters' skulls '''[[BodyHorror have no eye or nose sockets, or even teeth]]'''. Granted, the characters' skeletons were most likely drawn sloppily and featureless because the developers figured that they shouldn't waste tons of polygons on something that the gamers will only see for a few frames, but ''still''!
* The GameOver screen for ''Sonic 3D Blast'': instead of the words "Game Over" simply flashing on screen after the last life is lost, the screen turns a pale blue as the letters for "Game Over" appear, set to the Game Over theme from ''Sonic 3 & Knuckles'', then at the very end, the screen just [[http://www.youtube.com/watch?v=7q236FqlgP4 shatters.]]
** The Genesis version of The Final Fight has been considered unsettling by some, due to taking place in a featureless black void.
* [[spoiler:Metal Sonic's]] [[TheStinger appearance]] in VideoGame/SonicTheHedgehog4[='=]s [[http://www.youtube.com/watch?v=WbSsMppR1A8 alternate ending]] is a bit unnerving, when [[JumpScare unexpected.]]
* One of the most creepy moments was the [[NothingIsScarier open interpretation]] of the [[MultipleEndings incomplete ending]] of the Game Gear version of ''Sonic 2'', in which Tails gets kidnapped by Dr. Robotnik. If you don't collect all the [[PlotCoupon Chaos Emeralds]] throughout the game, then you do not gain access to Crystal Egg Zone and have the [[DownerEnding bad ending]] [[http://www.youtube.com/watch?v=IZ19n421nBc credits]], at the end of which Sonic looks up and sees [[spoiler:a constellation of Tails in the sky]], which could very well pertain to [[spoiler:Tails' presumed death]]. Youtube user LetsPlay/WhoIsThisGit [[http://www.youtube.com/watch?v=HCQZOh2faww had a field day with that one.]]
* The bad ending of ''VideoGame/KnucklesChaotix'': [[https://www.youtube.com/watch?v=hIApBr6xoK0 The final boss overlooking a city (possibly Newtrogic High Zone) in flames]].
** The final boss is rather terrifying, with its blood-red color scheme and vicious fangs plus copious shading that gives it a truly menacing appearance.
** And if the player fails to collect all Chaos Rings, ''he gets right back up after his defeat'' and everything goes red -- [[GoryDiscretionShot we can assume that he's viciously tearing you apart]]. Cue aforementioned BadEnding.
* The Game Gear game ''Tails Adventure'' has a boss where you're trapped in a room and must use Tails's mini-robot to defeat Dr. Fukurokov. To do this, you have to navigate the robot through a tiny maze to reach a rock you must push onto the boss's head. He looks startled momentarily, then falls on his back and stays that way.
** ''Tails Adventure'' in general can be pretty jarring, going from robotic enemies for most of the ''Sonic'' series to live ones here. Noteworthy is [[OverlordJr Speedy's]] second boss fight. [[DefeatEqualsExplosions He blows up.]] And seems to visibly spasm while it happens.
* The arcade game ''[=SegaSonic=] the Hedgehog'' can be a little frightening. The story of the game is that Dr. Eggman[=/=]Robotnik has captured Sonic, Mighty, and Ray and puts them on his island that contains various {{death trap}}s. The object of the game is to run from the beginning to the end in each level in one piece. The catch is the aforementioned traps such as giant tornadoes, gigantic stalactites, spike walls, and circular blades (which Eggman can activate with a push of a button). There are more in the game; the point is that it shows how determined Eggman is and how far he will go to destroy Sonic and friends. You can hear in his voice during the course of the game that he really loves [[http://www.youtube.com/watch?v=z0Qr0kSXGEg torturing Sonic.]]. That scream he lets loose at 1:14 proves this.
* Sonic X-Treme, even though it is cancelled and this soundtrack may not be real, has [[http://www.youtube.com/watch?v=AggTsbBNUFo a pretty unsettling game over tune]].

[[folder: Non-Game Media]]
* Super Sonic in ''ComicBook/SonicTheComic''. Unlike in the games where Super Sonic is merely a [[SuperMode super-powered form of Sonic's]], he is Sonic as a [[SuperpoweredEvilSide super powered sociopath]] who wants nothing more than to kill and torture anything in his path, preferably slowly.
* The plot of ''Literature/SonicTheHedgehogInRobotniksLaboratory'' is Robotnik transforming animals into robots. Not too different from his normal plans, you may think; but rather than capturing animals and throwing them into machines, he's invented a device that'll transform the physical body into something "useful". For example, Johnny Lightfoot is transformed into a mop. Worst of all, the creature that is transformed is [[AndIMustScream fully conscious and aware]].
** Then there is a slight malfunction and the machine transforms a group of crawlers into "something resembling crawlers but made out of spaghetti", and they slowly fall apart with shocked expressions on their faces.

[[folder:Fan Works]]
* ''Sonic 2: Long Version'' has [[http://www.youtube.com/watch?v=BaQvhLnBLmY Genocide City Zone]], a dark gloomy city with a FacelessEye cloud looming over it, and [[DeadGuyOnDisplay chained skeletons hanging from the ceiling]] that look like rotten corpses with their brown rags. At least the original soundtrack of the game is kept, so the music works as a NightmareRetardant.
* The online continuation of ''Sonic the Comic'' shows what happened to Robotnik after the ''Sonic Adventure'' adaptation -- reduced to a drooling madman who is said to "rarely sleep" and is focused entirely on revenge on Sonic. And as of #250, [[spoiler:he's been [[http://www.stconline.co.uk/250/comics/comic114_sml.jpg wired into a Drakon war computer]], speaking through a synthesiser, and it only ''partially restored his sanity'']].
-->[[spoiler:'''Robotnik:''' The Drakons found me a broken shell, but then they placed me in this machine. [[WetwareCPU My brain is the control chip of a vast supercomputer.]] On a whim, I can direct millions of my robots to attack wherever I choose. All that they see, I now see.]]
* ''VideoGame/SonicExe'' started as an urban legend of an unreleased Sonic game on the UsefulNotes/SegaCD that was possessed by some demonic force which caused the game to change into a hellscape, with Sonic having [[BlackEyesOfCrazy black eyes and red pupils]] that bled and a SlasherSmile. Of course, fan games and ROM hacks based on this urban legend were made, each one more nightmarish than the last.
** One in particular is ''[[BlatantLies An Ordinary Sonic Rom Hack]]''. The game begins like normal until you push start and the title screen is replaced with a more nightmarish version. The actual gameplay remains unaltered until [[ThirteenIsUnlucky thirteen seconds]] pass, then the zone you're in transforms into something more akin to hell, with immortal enemies and rings that actually reduce your ring count. After a while, an evil Sonic doppelganger appears and chases Sonic, accompanied by [[HellIsThatNoise an off-key version of the drowning theme]], and if he catches you, you die. If the player gets a GameOver, the game returns to the SEGA logo... until a digitized render of the "I AM GOD" picture appears with a distorted version of the SEGA voice. [[https://www.youtube.com/watch?v=ThSpW33w2gA Witness the horror for yourself.]]
--> '''''[[AGodAmI I AM GOD]]'''''
* ''[[http://malware.wikia.com/wiki/Sonic_Gather_Battle Sonic Gather Battle]]'' is frightening on two levels, the first important one being that the game is malware. When installed and launched, the game's DRM will send information about the player's computer to a remote server and monitor for either cheat engines or searches for cheats in a browser. If it detects either a cheat engine or searches for cheats, the DRM will interfere with the game in a nightmarish fashion: either changing the backgrounds to black and blue and adding red ghost enemies that render the game difficult to play, or changing the background red and adding creepy eyes before frightening ghosts invade the screen, followed by a "YOU DIED" screen. All this for the stupidest of reasons: the game's creator was paranoid about people stealing his sprite edits ([[EpicFail it didn't work]]). The game has since been discontinued, all official download links are now dead (other download mirrors exist, but should be avoided), and the game has been rendered unplayable to everyone regardless of whether they did anything to trigger the DRM. The DRM's frightening effects [[https://www.youtube.com/watch?v=LFeYQXDSHJ0 have been recorded for posterity]], and the developer has been permanently banned from all future Sonic Amateur Game Expos.
* Metal Sonic is a creepy character when you think about him. How do you make him worse? Well, there's one fan theory as to why Metal Sonic remains Robotnik's greatest challenge to Sonic: it's because Metal Sonic is no robot, but actually a time-traveling, [[UnwillingRoboticisation roboticized]] Sonic from the BadFuture seen on Little Planet. That's an unnerving idea in itself, that Sonic's deadliest rival is actually a FallenHero version of himself from an alternate timeline, but it gets worse: this same theory postulates that Metal Sonic is trapped in an AndIMustScream situation, with his consciousness locked away amongst the programming, aware of his actions but unable to control himself... worse still, being stranded in this alternate timeline with a doppelganger of himself may be driving him insane, and his hatred of Sonic is now less a matter of programming, and more a broken, twisted mind struggling to deal with a situation it can't handle. There's a video on the theory [[https://www.youtube.com/watch?v=RtgDdLqCZCg here]], which really highlights just how unsettling it is.
** [[Music/BlackSabbath So Sonic was turned to steel by a great magnetic field?]]