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[[quoteright:350:[[VideoGame/SonicAdventure http://static.tvtropes.org/pmwiki/pub/images/perfect_chaos.jpg]]]]
[[caption-width-right:350: And 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/SonicShuffle Sonic Shuffle]]
* [[NightmareFuel/SonicAdventure2 Sonic Adventure 2]]
* [[NightmareFuel/ShadowTheHedgehog Shadow the Hedgehog]]
* [[NightmareFuel/SonicTheHedgeHog2006 Sonic 06]]
* [[NightmareFuel/SonicLostWorld Sonic Lost World]]
!!Other entries:

[[folder: General]]
* [[http://www.youtube.com/watch?v=9Yw5jkAHgME The infamous drowning theme]] frequently reduced players (although some players don't feel so frightening) to tears while playing through Labyrinth Zone in VideoGame/SonicTheHedgehog, if only because of how [[JumpScare louder-in-comparison and unexpected]] it was. 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 Colours 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 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 predictable results.
** Tails lampshades this in ''VideoGame/SonicGenerations'' by saying the water in Chemical Plant Zone makes him really nervous.
* 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.]] It was kinda for the better, though, since even the original Japanese Robotnik (named Eggman) set up huge polluting factories that ruined the environment, which was in direct contrast with his playful and cute appearance.
* 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...]]
* 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.
* Squish traps, especially in abundance. Especially knowing that rings, shields, and even Super Sonic status will not protect you.
* 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 Metal Sonic Kai and his gradual transformation into Metal Overlord respectively.

[[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 CD]]
* The US soundtrack in general -- namely, [[http://www.youtube.com/watch?v=HcwyDL3-Qqo the boss music]] and the [[http://www.youtube.com/watch?v=YM8qx-HdY5c Game Over music]]. The boss music is simply creepy, but the Game Over music is outright scary (with the sound of evil laughter). This is in sharp contrast with the soundtrack's JP/EU counterpart, as there those two tracks aren't scary; the JP Boss music has an AffablyEvil feel to it, and the JP Game Over music (a slowed-down, tempo down sample of the main theme "You Can Do Anything") is more like SarcasticClapping in musical form.
** Worth mentioning is the fact that, according to [[http://segaretro.org/Spencer_Nilsen?rdfrom=%2F%2Finfo.sonicretro.org%2Findex.php%3Ftitle%3DSpencer_Nilsen%26redirect%3Dno#Sonic_CD_.28U.S._edition.29 this page]], the US boss theme wasn't composed by Spencer Nilsen (the main composer for that version), but rather by David Young. The main songs Young had a hand in were the ones for Collision Chaos and Metallic Madness, which are more atmospheric than anything, especially compared to much of Nilsen's music. However Nilsen did make the Game Over music.
** On the other hand, the boss music is used to nightmarish effects in the game's [[DebugRoom hidden sound test]], resulting in [[http://www.youtube.com/watch?v=UuRbrscizjE this scary]] EasterEgg.
** However, while the main tune of the Japanese Metallic Madness Bad Future music sounds catchy, the laughter from the Japanese boss music is in this song and actually sounds evil this time. And also, the robotic voice throughout the song. It almost sounds like he's [[TheFourthWallWillNotProtectYou talking directly to the player through the fourth wall]]. Despite [[{{Narm}} sounding cheesy]], [[NarmCharm it somehow manages to work]].
--->''"You can't do anything, so don't even try. Get some help. Don't do what Sonic does. Sonic, dead or alive, is mine!"''
** 5/7 of the US Bad Futures are disturbing in their own way. Palmtree Panic Bad Future is a depressing remix of the Present music, Collision Chaos is similar to the Present but even darker, Tidal Tempest is just DEPRESSING (debatably more so than the Palmtree Panic one), Quartz Quadrant is what you get when you take the Good Future and turn it into a disturbing heavy metal rendition, and Metallic Madness Bad Future is not so different from the Boss music.
* If the game is not paused or is idle for three minutes, Sonic says "I'm outta here!" and jumps off the screen, resulting in an instant NonStandardGameOver; if you are using the US soundtrack, the aforementioned terrifying GameOver music comes into play. If you did not expect it, it's pretty {{j|umpScare}}arring. Even without that, the implications are frightening: Sonic gets so bored of waiting around that either he gives up on saving Little Planet or [[DrivenToSuicide kills himself]].
* Using a code on the main menu screen will bring up Sound Test. By using the numbers 46, 12, 25; you get a wallpaper of Sonic with creepy human-like face coupled with the US boss music playing and a very demonic Japanese message that states:
-->''"Fun is infinite. Sega Enterprises. ~ Majin"''[[note]]this being [[http://legendsoflocalization.com/qa-whats-the-deal-with-that-creepy-sonic-cd-secret/ the nickname of developer Masato Nishimura]].[[/note]]
** The "Majin" part of the message is often understood as the Japanese word for "demon".
** This screen is said to have appeared during early pirated copies of the game. Then [[DigitalPiracyIsEvil Digital Piracy Is]] [[DealWithTheDevil Literally Evil]]!
* Metal Sonic projector, which shows a hologram recording of Metal Sonic ''[[KickTheDog beating up helpless animals.]]'' All of this while [[TearJerker a bird desperately flies around Metal Sonic, unable to do anything.]]
* On the subject of Metal Sonic, his race with him. If you fall too far behind, Eggman will hit you with a massive laser. Those who simply expect a loss of Rings are in for a shock when they discover that the laser is an unconditional OneHitKill.

[[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...]]
* SonicSpinball in general is the franchise's NightmareFuelStationAttendant: 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 acessed through hacking are all sorts of nightmare fuel, WARNING: SensoryAbuse

[[folder: Sonic The Hedgehog 3 & Knuckles]]
* 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 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 [[{{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:''' 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 to 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 naturally triggers Chaos' berserk button 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 giant alligator in Lost Jungle.
* 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.

[[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 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 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]]
* The Digital Dimension track, the first half of which is a hellish landscape with creepy gargoyle statues and weird ghost/skeleton hands that try to drag you into a pit. InUniverse, Storm the Albatross states to be scared of it. Rumor has it that this track nearly gave the game an E10+ rating.
* 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 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 its goes OneWingedAngel, its 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 attacking Dark Gaia's eye, [[{{Squick}} causing it to leak green blood]], this is also the reason why the game received ESRB rating of E10+.
* In the opening, Eggman actually manages to split the Earth apart into seven piece.
** 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 [[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 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 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. About 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.

[[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.]]
* Doctor Robotnik's Mean Bean Machine in Scenario Mode. Whenever you're losing, your enemy will have this look on their face that makes them seem like they want to molest you.
* 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. 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 a pretty unsettling game over [[http://www.youtube.com/watch?v=AggTsbBNUFo]]

[[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 focussed 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.]]
* ''Sonic.exe'' 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 get a GameOver, the game returns to SEGA logo... until a digitized render of the "I AM GOD" picture appears with a distorted version of SEGA voice. [[https://www.youtube.com/watch?v=ThSpW33w2gA Witness the horror for yourself.]]
--> '''''[[AGodAmI I AM GOD]]'''''

[[folder: Non-Game Media]]
* [[NightmareFuel/SonicSatAM See here]] for NightmareFuel from ''WesternAnimation/SonicSatAM''.
* [[NightmareFuel/SonicUnderground See here]] for examples from ''WesternAnimation/SonicUnderground''.
* [[NightmareFuel/SonicX See here]] for examples from ''Anime/SonicX''.
* "Sonic's dad [[WasOnceAMan isn't really a Mobian anymore.]] [[SelfMadeOrphan My dad simply isn't]]". Scourge is just plain creepy.
** [[FridgeHorror And is effectively what Sonic would've been if he turned evil.]]
* Eggman's descent into crazy in both the American comics and the UK ones is just unsettling. Good thing [[http://i54.photobucket.com/albums/g116/Orengefox/SnoopingAsUsual-1.png some]] [[http://img838.imageshack.us/img838/3887/itsfromtheshow.jpg things]] just tell you the writer is OneOfUs.
** And then when he starts regaining his composure, it turns out he [[http://images3.wikia.nocookie.net/__cb20100311220202/archiesonic/images/thumb/9/94/Th_DrIvoRobotnik-1-2-.jpg/642px-Th_DrIvoRobotnik-1-2-.jpg kept a few features from his original body.]]
** The Order of Ixis taking control of Ixis Naugus in ''Sonic Universe'', making him an even more crazy and more dangerous being in the process. [[http://images.wikia.com/archiesonic/images/b/ba/Ixis_Naugus_True_Form.jpg It's even starting to show physically.]]
* [[OmnicidalManiac Enerjak]]. An evil godlike AlternateUniverse Knuckles who threw the world into chaos after Sonic was unable to stop him ([[TheBadGuyWins yep, you read that right]].) Anyone who has the misfortune to lose against Enerjak has his/her "Core" ([[SoulJar which is basically their soul]]) [[AndIMustScream extracted from his/her body by him]], which he can use to [[http://images1.wikia.nocookie.net/__cb20110429040129/archiesonic/images/5/5f/Prelates.jpg create evil robotic clones of them called Prelates]]. [[http://images1.wikia.nocookie.net/__cb20110224070925/archiesonic/images/1/14/Photo.png Just look at his body count]], which includes [[TheHero Sonic]], [[MadScientist Eggman]], even ''[[NighInvulnerable Shadow]].''
* Having the resident BadAss AntiHero Shadow [[http://i23.photobucket.com/albums/b389/Rae_Logan/scaryshadowmoment.png screaming mutely and twisting in pain was somewhat disturbing.]]
* 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 plan you may thing; but rather than capturing animals and throwing them into machines he's invented a device that'll transform the physical body into some "useful". For example Johnny Lightfoot is transformed into a mop, and worst of all the creature that is transformed is 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", they slowly fall apart with shocked expressions on their faces.

'''5'''...'''4'''...'''3'''...'''2'''...'''1'''...'''0''' '' [[HaveANiceDeath (drown)]]