History DummiedOut / SonicTheHedgehog

* There are two unused cutscenes in the game: [[https://www.youtube.com/watch?v=tEwkfHkudpE one]] of Eggman berating E-102 Gamma for failing to complete Final Egg, and [[https://www.youtube.com/watch?v=11sQUywrnUw another]] of Amy below the Egg Carrier deck which was never dubbed into English.

* ''VideoGame/SonicAdventure'' had some details changed in localization; in the Japanese version, the title screen is brighter and static, and Sonic's feet blur at top speed like the WheelOFeet from the Mega Drive games. There's also the infamous cowgirl billboard in Casinopolis that was replaced with a generic marquee in the International version.

* [[https://www.youtube.com/watch?v=q8Im0r86dKE Several lines of dialogue]] were either cut or replaced with alternate takes.

** [[ScrappyMechanic Sonic bounces off walls if he runs into them, and Tails loses rings for the player when hit.]]

** The build still has a lot of assets left over from ''Sonic 1'', including music and Green Hill's tiles plus some raw code left within.

* ''[[VideoGame/SonicTheHedgehogCD Sonic CD]]''[='=]s ending video and the D.A. Garden screen hint at a scrapped [[ShiftingSandLand desert level]]. Design and programming of this game's levels were given to individual people; this level seems to have been scrapped because [[ScheduleSlip its designer couldn't finish it on time.]]

** There are three level slots for scrapped levels. Hidden Palace Zone and Wood Zone are semi-playable, but many areas can't be reached without debug mode. [[Hidden Palace https://www.youtube.com/watch?v=LZAIyzRAyug]] is about two-thirds complete, while [[http://www.youtube.com/watch?v=NWf_XmEu9cA Wood Zone]] has a garbled and very incomplete layout. The third one is a level entry for the aforementioned Dust Hill, which actually leads to Mystic Cave; because this build was sent to gaming press, Mystic Cave was often called by the former's name.

* Green Hill's unused wrecking ball object returns. While still unused, it can be placed in DebugMode and behave logically as an obstacle.

* ''VideoGame/KnucklesChaotix'' has at least one character, dubbed [[FanNickname "Wechnia"]] by hackers, plus several items and level features cut from the final release.. ''Chaotix'' began development as ''Sonic Crackers'', an internal engine test featuring Sonic and Tails; it can be inferred that since Mighty is ultimately a spriteswap of Sonic, "Wechnia" is Tails. He was probably removed because two flying characters in ''Chaotix'' would be redundant and [[GameBreaker throw off the game balance]].

* From test environments floating far away from normal access, to lines involving Perci, one of the [=NPCs=], still activating during one area of the game as if she was playable (even though she just stands around and gives you quests at best), ''VideoGame/SonicBoom: Rise of Lyric'' has traces of content left over from the game's TroubledProduction all over the place.

* Super Sonic also had text to recap the story events, like the other six characters. This ''can'' be viewed legitimately if you grab Sonic's optional upgrade in the Last Story and exit the game, but the recap [[UnwinnableByMistake freezes the game and corrupts your save file]].

The ''Franchise/SonicTheHedgehog'' series has enough that [[WikiRule it has]] [[http://info.sonicretro.org/ its own wiki for it.]]
* ''VideoGame/SonicTheHedgehog1'':
** The original game had its fair share of removed work, most notably the enemy "Splats the Rabbit", who never appeared without hacking, yet [[WolverinePublicity whose image got into the promotional artworks, and turned up in the comics and toy lines for it]]. There's also the checkered ball obstacle, which had its graphics reused for Robotnik's wrecking ball and was sort of brought back for use in the ''Sonic 2'' prototypes.
** Going into debug mode in the special stages in the first game, and teleporting yourself outside the maze can produce some interesting results. You will eventually run into random graphics of powerups that were never used in the final game, including a 'W' powerup, '1 zone', '2 zone', and '3 zone' powerups, and an extra life powerup, the latter of which is mentioned in the manual.
** The [=iOS=] port cleans up and adds coding for most of the game's unused objects... but they still aren't used.
** It seems that the Game Gear and Master Systems versions of the game were originally supposed to have the same levels as the Genesis/Megadrive versions, as deep within the Master Systems game code there exists [[http://www.youtube.com/watch?v=fwXkhaqrt6c an unused 8-bit rendition of the Marble Zone theme]].
* ''VideoGame/SonicTheHedgehog2'':
** Quite a few different prototypes of ''Sonic 2'' have been found. Two in particular are quite interesting: The first one discovered, the so-called Simon Wai prototype (named after the person who released the ROM to the Sonic community; he in turn found it on a Chinese ROM site) is a dump of a fairly late build that was stolen from a toy fair in New York in 1992. The second, even earlier, is the "Nick Arcade prototype", which seems to match a build used on an episode of ''Series/NickArcade'' (starring [[Series/ClarissaExplainsItAll Melissa Joan Hart]]!) There were later at least six more late-development prototypes of Sonic 2 that were discovered, all of them created between the Simon Wai Proto and the final launch version of the game.
** There are many, many unused animations for Sonic hidden in the game code. Some of these were later used to create the new spritework for ''Sonic Mania'' and most of them can be found buried in the code for the Taxman and Stealth remaster.
** Hidden Palace Zone's music can be found in the SoundTest in ''Sonic the Hedgehog 2'' and the level layout is also contained in the ROM. The sprites and collision data, however, aren't, which means that hacking to access the level produces a very garbled screen where Sonic and Tails fall and die. It also contains the palette for the further-deleted Wood Zone. However, a reimagined Hidden Palace Zone, was made available in the {{Android|Games}} and {{iOS|Games}} ports [[http://www.joystiq.com/2013/12/11/remastered-sonic-the-hedgehog-2-hits-android-ios-tomorrow-with/ after over 20 years]], courtesy of [[PromotedFanboy promoted fanboys]]. [[http://www.youtube.com/watch?v=T3pWvN731-E Here is a look]]. It uses the music that was used in the beta version, which is Mystic Cave Zone's 2 player music.
** The rerelease also dummied out [[http://info.sonicretro.org/Game_Secrets:Sonic_the_Hedgehog_2_%282013%29 another level]] designed to be a one act BossRush. A BossRush still exists in the rerelease, but it's more segmented.
** Hidden Palace Zone and Wood Zone are semi-playable in the leaked ''Sonic 2'' "Simon Wai" prototype, though many areas are inaccessible without the debug mode. The former is about [[http://www.youtube.com/watch?v=LZAIyzRAyug two-thirds complete,]] and the latter [[http://www.youtube.com/watch?v=NWf_XmEu9cA consists only of random fragments.]]
** The beta also had the blank Genocide City Zone, a planned single act zone whose map became Metropolis Zone Act 3. The story goes that one of the (Japanese) designers wanted a word that sounded "dangerous" and [[SurpriseCreepy overshot]]. Once they realized what it meant they quickly changed that name to Cyber City before time constraints led to them making it into Metropolis Act 3. They didn't have enough time to give Cyber City all its own graphics, but they didn't want to waste a perfectly good level map.
** A promotional screenshot showing a desert-themed zone baffled fans for years. In the "Simon Wai" prototype, there is a level select entry for "Dust Hill Zone," which in fact led to Mystic Cave Zone. Brenda Ross, the level's designer, confirmed its name to be "Dust Hill Zone" in an interview. She had also planned a winter-themed level [[PaletteSwap that would reuse most of its graphics]] with the cacti replaced by Christmas trees.
** Death Egg Zone contains an accidental example -- when you're fighting the Silver Sonic, Robotnik is watching from a little window in the center of the screen. Now, he has an animation to giggle evilly when you take damage, and it's all programmed in and implemented and everything, but you still won't ever see it without debug mode, because Death Egg Zone is a DroughtLevelOfDoom with no rings, so the very first time you take damage, you'll die, freezing all animations.
* ''[[VideoGame/Sonic3AndKnuckles Sonic the Hedgehog 3]]'':
** ''Sonic 3'' seemed to be ''full'' of this sort of thing - unreachable areas, half-implemented bosses, enemies which appeared in the manual but not in the game proper, etc. - until the ExpansionPack ''[[VideoGame/Sonic3AndKnuckles Sonic & Knuckles]]'' was released, and gamers were allowed to buy [[OneGameForThePriceOfTwo the second half of the game]]. There are still a few mysteries that appear in the DebugMode, though, like a surfing Sonic, and a giant cluster of red spheres which can be affected by messing with the second controller and was probably used to test the Special Stage pseudo-3D graphics. Surfing Sonic was meant for the intro, but was pretty obviously scrapped because someone on the dev team decided that Sonic going {{super|Mode}} to infiltrate the island [[RuleOfCool would be more interesting.]]
*** It also [[JustifiedTrope justifies]] the [[BagOfSpilling loss of the Chaos Emeralds]] from the last game, just as [[VideoGame/SonicTheHedgehog1 Sonic 1]] did in its GoldenEnding.
** This also works ''backwards'': When playing Launch Base Zone (the final level of ''Sonic 3'') in ''Sonic 3 & Knuckles'', the original end boss and ending sequence of ''Sonic 3'' (including the original end credits music) are omitted in favor of carrying straight on to the first level of ''Sonic & Knuckles'' instead. It's still possible to fight this boss by playing ''Sonic 3'' individually as Sonic or Tails, or by playing ''Sonic 3 & Knuckles'' as Knuckles.
** There's a Gold Chaos Emerald Special Stage, which can only be accessed via Debug Mode and is extremely difficult. You could try it by using debug, but you'll lose unless you have no eyelids. Some people think it might have been intended to be the Master Emerald, although this is rather unlikely.
* ''VideoGame/Sonic3DBlast''
** Several known prototypes of this game exist, and the fourth prototype had [[http://www.youtube.com/watch?v=rpn9Wh9ghkw an unused boss theme]] that would later show up as the normal boss theme in ''VideoGame/SonicTheHedgehog4: Episode I''.
* ''VideoGame/SegaSonicTheHedgehog'' has a nearly-complete set of unused sprites of Robotnik as he looked in the cartoons and Archie comics of the time. It's possible this sprite work was intended to be used for the Western releases, but ultimately Robotnik ended up using the same sprite artwork in all versions of the game.
* ''VideoGame/SonicAdventure'' contains an unusually large amount of unused content, second perhaps only to ''Sonic 2''.
** In late 2013, an "[=AutoDemo=]" prototype of the game was released. It comes from a very early period of development and contains a vast amount of changes. A quick summary:
*** By far, the most significant discovery was of [[http://sost.emulationzone.org/sonicadventure/beta_windy/windy1.jpg the prototype Windy Valley]], which plays ''absolutely nothing'' like the final version. Its level design features wavy terrain and open spaces which suggest that the game originally relied more on physics and exploration, similar to earlier Sonic games and other 3D games like ''VideoGame/SuperMario64''. The level was broken even in the [=AutoDemo=] itself, as it referred to pointers even older than the [=AutoDemo=], and had no data left other than the models, but the fans quickly produced a [[https://www.youtube.com/watch?v=mk56zpP9-JQ playable mod]].
*** Some of the wide-open parts of this level were cut off and used as the Egg Carrier's Chao Garden early in development. The level is also seen briefly in Amy's flashback, albeit in pre-rendered and edited form.
*** Three test levels were found. While test levels aren't uncommon, these three had various sloped structures that, again, suggested a greater reliance on weight-based physics than the final game.
*** Knuckles has many more combat-oriented animations, such as the [[https://vignette1.wikia.nocookie.net/sonic/images/b/b3/UppercutSA.jpg/revision/latest?cb=20131010230320 uppercut combo]] seen in certain promotional material.
*** Speed Highway, Emerald Coast, and the Egg Carrier have different object placement.
*** Lost World has a different snake segment and the doors that opened to different areas were originally obstacles that could crush Sonic.
*** Knuckles' Speed Highway has a strange pit in the middle of the area with a clock tower inside; also seen in some promotional screenshots.
*** The Tokyo Game Show character selection works properly, and Knuckles even has an in-game tutorial that teaches him how to glide.
*** Sonic's Light Speed Attack works differently. After charging it up, Sonic goes into a unique "ready" stance where he kneels. Then he will charge at targets one-at-a-time, with the player choosing which targets to follow. It all looks rather awkward and unfinished, and was understandably changed by the final release.
** During the Sky Chase segment, there was originally supposed to be a [[https://www.youtube.com/watch?v=Yx-5O8pH3Jw two-headed robot dragon]] that chased the Tornado. The model for the enemy still remains on the disc, and modders were able to reconstruct it to the point where it actually worked. Unfortunately it doesn't do anything other than follow you, having no programmed attack moves. However, [[http://sost.emulationzone.org/sonicadventure/dragon/dragon2.jpg pre-release screenshots]] do show it breathing fire, so presumably it could attack at some point.
** Super Sonic was also originally intended to be playable outside of the Last Story, [[http://www.youtube.com/watch?v=KyXIlPBANzY as proven by this Tikal clip.]] Similar to the classic games, the player would collect 50 rings, jump, and press the action button in midair. In the final game, pressing action in mid-air does actually have a minor effect: it cancels the spin and jump.
** The game had minor revisional differences; the original Japanese version was released in 1998, but Sonic Team had a few months to further polish the game for its International release. The title screen is brighter and static in the original Japanese version, and Sonic's feet have a unique blurring effect that resembles the WheelOFeet he has in the classic games. There is also an infamous cowgirl billboard in Casinopolis that was replaced with a generic marquee in the International version.
* ''VideoGame/SonicAdventure2''
** In Sky Rail Zone, one of the platforms near the end of the level has an invisible section on its right-hand side. It would appear that another path was originally present here, and rather than remove or even dummy out this path, Sega simply made it invisible, so that gamers were unlikely to stumble upon it and wouldn't be able to follow it very far if they did.
** Meteor Herd, one of Knuckles' levels, contains an invisible rail. Rails can only be used by Sonic and Shadow.
** Several levels have distant components, such as alternate goal rings or tiny, almost invisible platforms, that the player can see in the extreme distance, but are impossible to reach without cheat devices.
** And to add more to the dummied-out bin, there were the Knuckles and Amy chao. They were both exactly like the Tails chao in terms of immortality, that both look somewhat like their namesakes and so forth, except that unlike the Tails Chao, both the Knuckles and Amy chao had no trigger to unlock either of them (even so, the Tails Chao [[OneGameForThePriceOfTwo required]] ''[[VideoGame/PhantasyStarOnline Phantasy Star Online Ep I]]'' and ''[[VideoGame/PhantasyStarOnline II]]'' [[OldSaveBonus to unlock it and]] [[GuideDangIt couldn't be done so in-game within]] ''[[GuideDangIt Adventure]]'') and because of this they had many rumors on how to unlock them among the debates on whether or not either exists. In truth they still exist and are fully functional, but both of them can only be unlocked by using Action Replay codes. Most likely, they were meant to be available through some kind of event, similar to the Franchise/{{Pokemon}} series' Mew and Celebi. If such an event was held was previously unknown, however, Wikipedia has claimed they were downloaded to player's memory cards in an event only held [[NoExportForYou in Japan.]]
** Metal Sonic is the only character [[http://www.youtube.com/watch?v=XGt__j7JOfc in this video]] whose victory screen after the fight doesn't glitch, since the game more or less treats the 2P alternate characters as as alternate skins of Sonic and Shadow with slightly altered stats in the Battle version (They literally were plain alt skins in the original game) Metal Sonic's victory scene is done correctly because as far as the game is concerned, he's Shadow. This can be observed in other stages and bosses, making this more an example of [[{{Pun}} Dummied In]].
** [[http://www.youtube.com/watch?v=q8Im0r86dKE There were also several lines of dialogue that were either replaced by alternative audio or outright cut in the final product.]]
** In the game, [[http://www.textures-resource.com/resources/sheets/1/640.png hidden in Rouge's textures,]] is a texture of her butt. Presumably, whatever cutscene the graphic artist expected this texture to show up in was cut to keep the rating down.
** The Chao Kindergarten was originally supposed to have a [[https://tcrf.net/images/thumb/b/bc/Sa2_ChaoLibraryLevel.png/320px-Sa2_ChaoLibraryLevel.png Library]] and a Chao Playground. Cut text implies the library would have been used to create new stories for the Chao Adventure VMU game, featured on the original Dreamcast version, while the playground was [[http://info.sonicretro.org/images/9/9e/Sa2kin_cophot2.png pictured]] in one of the kindergarten photographs, but later removed from all subsequent ports. Through piecing together bits of data, fans were able to give us an idea of what it would have [[https://tcrf.net/images/thumb/7/76/SA2ChaoPlaygroundRender.png/640px-SA2ChaoPlaygroundRender.png looked like.]]
* ''VideoGame/SonicMania''
** Green Hill Zone has a fully-functional Wrecking Ball object based on the one that did nothing in the original Sonic the Hedgehog's version of Green Hill Zone. In ''Mania'', as part of a MythologyGag, you can place it in Debug Mode and it will behave logically as an obstacle.
** There are a number of interesting details and features camera-locked just outside of player view and only accessible with Debug Mode. For example, Press Garden has the word "Hello" written backwords somewhere inaccessible below the main level route, Hydrocity Act 1 has a concealed texture panel at the far top-left of the level close to the player's spawn point, and Knuckle's portion of Lava Reef Act 2 actually extends well beyond the camera lock point and reveals that it was originally planned to include the Hidden Palace Mural level segment.
** Hidden in the data files are some unused sprites and assets from the Taxman & Stealth remasters of ''Sonic'', ''Sonic 2'', and ''Sonic CD'' that were used to test the engine. There are also leftovers from the preview builds, like the COMING SOON 2017 screen from the end of a demo, original level layouts used for the teasers and previews, and even data for the original SEGA level maps for the Classic zones.
* Other
** ''VideoGame/KnucklesChaotix'' has at least one dummied out character, which the hacking community has dubbed [[FanNickname Wechnia]], and a number of items and level elements that weren't implemented in the final version of the game. This is because ''Chaotix'' was meant to be "Sonic Stadium", but somewhere along the lines developers and executives decided that the gameplay was too divergent from the previous games to keep with the idea. If you compare the sprites from the unreleased ''Sonic Stadium'' (also known as Sonic Crackers) closely, it's clear that Mighty is a sprite-edited Sonic, and actually shares moves and gameplay properties (he is the fastest character in the game, and in most games made after this one Sonic can wall jump), and "Wechnia" is Tails (he had the right palette in a rather early beta of the game, and in an even earlier version, he and Sonic both have character portraits). Tails was probably removed from the game because having two flying characters would be redundant and overly {{Game Break|er}}ing. The dummied out concept of a hub world made its way back into several later games, such as ''VideoGame/SonicBattle.'' In addition more traditional Sonic level aspects such as loop de loop platforms are found in prototype versions (albeit working improperly), but are absent in the final product (likely due to programming issues). Multiple other unused graphics are also found in the final game or its betas (such as bubble areas, implying water areas were intended at some point, and graphics of what seem to be an unused cutscene, including Super Sonic and the Tornado).
** An early version of the level music "Sunset Park 3" can be found inside the SoundTest of ''Sonic Chaos''. It was not used in that game, but was brought back for ''Triple Trouble''.
** In the UsefulNotes/GameGear version of ''Sonic 2'', the SprintShoes are clearly marked inside the manual, and yet they never appear in the game. The powerup only makes a single appearance in the Master System version of the same game, and is replaced with a box of rings in the Game Gear release. Furthermore, it was probably once intended that Tails be playable in this version of ''Sonic 2'', as careful searching reveals that Tails has extraordinarily detailed sprites for a non-playable appearance, even including his IdleAnimation.
** In ''VideoGame/SonicTheHedgehog2006'', the "Super Sonic" gem is partially in the final game, and the hacking community have found an actual transformation sequence for Sonic during gameplay. However, coding to actually allow one to ''play'' as Super Sonic isn't present.
** Super Sonic's story also had text that recapped what happened in the story, like what happens with the other six characters. In a subversion, this ''is'' possible to view if you grab Sonic's optional upgrade in the Last Story and then exit the game, but after playing said recap scene, the game freezes, [[UnwinnableByMistake forcing you to create a new save file if you want to complete the game]].
** One example from ''VideoGame/SonicTheHedgehogCD'' that many people miss is the unnamed desert level. This level shows up in the ending video and on the interactive SoundTest via a "world map" option, but since level design and programming were given to individual people, and the person in charge of this level was late in finalizing the look of the level, it was dropped late in development. There was, according to some interviews, yet another level planned for the game, but it didn't even get past concept phase. Furthermore, the PC version has all the levels contained in separate folders and one is conspicuously missing, R2, so that it goes R1, R3, R4, etc. The level is glimpsed in the ending animation, however, featuring an enemy that looks a hell of a lot like the first boss from ''Sonic the Hedgehog 2'' for the Game Gear, or rather, that game has a boss that looks like an enemy from ''Sonic CD''. This legacy was actually carried on in the downloadable remake in 2011, with [[http://www.sonicstadium.org/2011/12/unused-desert-dazzle-stage-image-found-in-new-sonic-cd-port/ an early screen of the desert level imagined into programming form found inside the games' memory]]. The reimagined "Desert Dazzle", along with a new final boss stage called "Final Fever" (itself sharing its name with the boss music for the final level, Metallic Madness, in the final version of both the original and remake) were planned as extras for the remake, but were turned down due to time restraints and SEGA's preference that the game not be altered too much from the original rendition.
** "R2" has been revealed as being modeled on Marble Zone, but extremely crude concept drawings of the zone have it resembling ''Sonic 2'''s Aquatic Ruin, but with rainbow waterfalls interspersed throughout the stonework. R2 was either dropped so early in development that it didn't warrant having a graphic on the DA Garden, or was meant to segue into the "Desert Zone," again given the graphic shown on the DA Garden. Both of these ideas were likely saved for the ''Sonic 3'' zones Marble Garden and Sandopolis.
** There are also a few alternate Twinkle Circuit tracks in ''VideoGame/SonicAdventure'' that can't be normally accessed, but may have been meant as UsefulNotes/SegaDreamcast [[DownloadableContent DLC]].
** In ''[[VideoGame/SegaSuperstars Sonic & Sega All Stars Racing]]'', the Final Fortress track descriptions talk about laser gates and a cameo that don't exist.
** In the Famicom ''VideoGame/SonicTheHedgehog'' bootleg port ''VideoGame/{{Somari}}'', the Scrap Brain Zone is dummied out. The game goes straight from Star Light Zone to the Final Zone.
** ''VideoGame/SonicGenerations'' was to feature Big the Cat in some capacity, to the point of having voiced lines, as confirmed by his voice actor. It can be speculated that he was to be the host friend for the "Speed Highway" stage (as ''VideoGame/SonicAdventure'' is his debut game) but was probably cut because he likely couldn't actually ''do'' anything in the stage, being a fisherman/power lifter in a stage with no water or physical obstacles.
** There is an unused Super Sonic bio that can be found in the game's files.
** In ''VideoGame/SonicHeroes'', Team Rose have the easiest and shortest levels in the game. However, since (as in the original ''Sonic Adventure'') they play through the same physical levels as the other characters, the entire level data for each stage still exists. Normally a wall or an impassible gap separate the end of Team Rose's levels from the the rest of the stage the other teams explore, but in two stages (Casino Park and Frog Forest) you can use a Team Blast and the subsequent speed boost to just barely clear the gaps, and continue the stages as normal. It's also possible for Team Rose to go into the ghost-filled well in Mystic Mansion, by hitting a particular switch and flying very carefully. What's interesting is that as you do so, the characters will continue to comment on things that they wouldn't even encounter playing the game normally (such as the VIP pinball room and the giant mushroom), indicating that there could be dummied out dialogue for the other stages as well.
** There are also [[http://www.youtube.com/watch?v=srBLlPB7N2Q unused voice clips]] of all the characters apparently reuniting with their team, and complaining about something being heavy. Hints at removed game mechanics?
** ''Sonic Gems Collection'', a compilation title that contained ''VideoGame/SonicTheFighters'', ''VideoGame/SonicTheHedgehogCD'', and ''VideoGame/SonicR'', had a few games that were planned to be included but were removed (not counting the US version's removal of the ''VideoGame/StreetsOfRage'' games). These games included the ''VideoGame/MonsterWorld'' Genesis games and ''Sonic Eraser'', the latter being a highly obscure puzzle game released on the Mega Modem peripheral in Japan. WordOfGod states that ''VideoGame/SegaSonicTheHedgehog'' was also considered at early stages, though eventually turned down due to the trackball controls making emulation difficult.
** ''VideoGame/SonicChronicles'' has the 5 Viral Chao. Said Chao were to be released in events, although only one was ever officially available. The rest of the Chao, excluding one, were included in the Japan release.
** From test environments floating far, far off in the sky away from anywhere you'd (normally) access, to lines involving Perci, one of the [=NPCs=], still activating during one area of the game as if she was a playable character (despite the fact that she just stands around and gives you quests at best), ''VideoGame/SonicBoom'' has traces of content left over from the troubled development of the game all over the place.

** There are a number of interesting details and features camera-locked just outside of player view and only accessible with Debug Mode. For example, Hydrocity Act 1 has a concealed texture panel at the far top-left of the level close to the player's spawn point, and Knuckle's portion of Lava Reef Act 2 actually extends well beyond the camera lock point and reveals that it was originally planned to include the Hidden Palace Mural level segment.

*** The TGS character selection works properly, and Knuckles even has an in-game tutorial that teaches him how to glide.

** During the Sky Chase segment, there was originally supposed to be a [[https://www.youtube.com/watch?v=Yx-5O8pH3Jw three-headed robot dragon]] that chased the Tornado. The model for the enemy still remains on the disc, and modders were able to reconstruct it to the point where it actually worked. Unfortunately it doesn't do anything other than follow you, having no programmed attack moves. However, [[http://sost.emulationzone.org/sonicadventure/dragon/dragon2.jpg pre-release screenshots]] do show it breathing fire, so presumably it could attack at some point.

** The game had minor revisional differences; the original Japanese version was released in 1998, but Sonic Team had a few months to further polish the game for its International release. The title screen is brighter and static in the original Japanese version, and Sonic's feet have a unique blurring effect that resembles the "wheel feet" he has in the classic games. There is also an infamous cowgirl decoration in Casinopolis that was removed in the International version.

* ''[[VideoGame/Sonic3AndKnuckles Sonic The Hedgehog 3]]'':
** ''Sonic 3'' seemed to be ''full'' of this sort of thing - unreachable areas, half-implemented bosses, enemies which appeared in the manual but not in the game proper, etc. - until the ExpansionPack ''[[VideoGame/Sonic3AndKnuckles Sonic And Knuckles]]'' was released, and gamers were allowed to buy [[OneGameForThePriceOfTwo the second half of the game]]. There are still a few mysteries that appear in the DebugMode, though, like a surfing Sonic, and a giant cluster of red spheres which can be affected by messing with the second controller and was probably used to test the Special Stage pseudo-3D graphics. Surfing Sonic was meant for the intro, but was pretty obviously scrapped because someone on the dev team decided that Sonic going {{super|Mode}} to infiltrate the island [[RuleOfCool would be more interesting.]]

*** 3 test levels were found. While test levels aren't uncommon, these 3 had various sloped structures that, again, suggested a greater reliance on weight-based physics than the final game.
*** Knuckles has many more combat-oriented animations, such as the uppercut combo seen in certain promotional material.

** In the Famicom ''VideoGame/SonicTheHedgehog'' bootleg port ''Main/{{Somari}}'', the Scrap Brain Zone is dummied out. The game goes straight from Star Light Zone to the Final Zone.

** Hidden Palace Zone's music can be found in the SoundTest in ''Sonic the Hedgehog 2'' and the level layout is also contained in the ROM. The sprites and collision data, however, aren't, which means that hacking to access the level produces a very garbled screen where Sonic and Tails fall and die. It also contains the palette for the further-deleted Wood Zone. However, Hidden Palace Zone, after over ''20 years'', was made available in the {{Android|Games}} and {{iOS|Games}} ports [[http://www.joystiq.com/2013/12/11/remastered-sonic-the-hedgehog-2-hits-android-ios-tomorrow-with/ in December 2013]]. [[http://www.youtube.com/watch?v=T3pWvN731-E Here is a look]]. It uses the music that was used in the beta version, which is Mystic Cave Zone's 2 player music.

The ''Franchise/SonicTheHedgehog'' series has enough that [[WikiRule it has]] [[http://info.sonicretro.org/ its own wiki.]]

** ''VideoGame/SonicChronicles'' has the 5 Viral Chao. Said Chao were to be released in events, although only one was ever officially available. The rest of the Chao, excluding [[GameBreakingBug one]] were included in the Japan release.

* ''VideoGame/SegaSonicTheHedgehog'' has two unused sprites of Robotnik as he looked in the cartoons and Archie comics of the time. It's possible this sprite work was intended to be expanded on for the Western releases, but ultimately Robotnik ended up using the same sprite artwork in all versions of the game.

** In the GameGear version of ''Sonic 2'', the SprintShoes are clearly marked inside the manual, and yet they never appear in the game. The powerup only makes a single appearance in the Master System version of the same game, and is replaced with a box of rings in the Game Gear release. Furthermore, it was probably once intended that Tails be playable in this version of ''Sonic 2'', as careful searching reveals that Tails has extraordinarily detailed sprites for a non-playable appearance, even including his IdleAnimation.

** There are also a few alternate Twinkle Circuit tracks in ''VideoGame/SonicAdventure'' that can't be normally accessed, but may have been meant as SegaDreamcast [[DownloadableContent DLC]].

** One example from ''VideoGame/SonicTheHedgehogCD'' that many people miss is the unnamed desert level. This level shows up in the ending video and on the interactive SoundTest via a "world map" option, but since level design and programming were given to individual people, and the person in charge of this level was late in finalizing the look of the level, it was dropped late in development. There was, according to some interviews, yet another level planned for the game, but it didn't even get past concept phase. Furthermore, the PC version has all the levels contained in separate folders and one is conspicuously missing, R2, so that it goes R1, R3, R4, etc. The level is glimpsed in the ending animation, however, featuring an enemy that looks a hell of a lot like the first boss from ''Sonic 2'' for the Game Gear, or should we say a boss that looks like an enemy from ''Sonic CD''. This legacy was actually carried on in the downloadable remake in 2011, with [[http://www.sonicstadium.org/2011/12/unused-desert-dazzle-stage-image-found-in-new-sonic-cd-port/ an early screen of the desert level imagined into programming form found inside the games' memory]]. The reimagined "Desert Dazzle", along with a new final boss stage called "Final Fever" (itself sharing its name with the boss music for the final level, Metallic Madness, in the final version of both the original and remake) were planned as extras for the remake, but were turned down due to time restraints and SEGA's preference that the game not be altered too much from the original rendition.

* ''VideoGame/SegaSonicTheHedgehog'' was a Japanese exclusive until the advent of emulation, but two unused sprites exist of the game code of Robotnik as he looked in the cartoons and Archie comics of the time. It's possible this sprite work was intended to be expanded on for a potential Western release.

** In the game, [[http://www.textures-resource.com/resources/sheets/1/640.png hidden in Rouge's textures,]] is a texture of her butt, [[WildMassGuessing either because they did it for some unknown reason or that a panty shot was planned but cut due to the fact that it would probably bump up the game's rating, and the fact that unless she changed her outfit, it would be very hard to make it work.]]