Sonic the Hedgehog CD (Sega CD)

Sonic the Hedgehog CD
Also known as: Sonic CD (US, EU) Developer: Sega Publisher: Sega Platform: Sega CD Released in JP: September 23, 1993 Released in US: November 19, 1993 Released in EU: October 18, 1993 This game has unused areas. This game has hidden developer credits. This game has unused objects. This game has unused graphics. This game has unused cinematics. This game has unused items. This game has unused sounds. This game has debugging material. This game has a hidden sound test. This game has a hidden level select. This game has regional differences. This game has a development article This game has a prototype article This game has a prerelease article This game has a bugs page

To do: A lot more due to the recent (work in progress) disassembly, check this Twitter/X account and here for more. Apparently there is this oddity with the Tidal Tempest palette as seen in this Twitter post. Could there be more like this? Old Collision Chaos chunks that appear to predate the 510 prototype are leftover in Wacky Workbench (YouTube video).

Sonic CD is just your average Sonic the Hedgehog game on a CD... that's what you're told, anyway.

Sub-Pages

Development Info

Prototype Info

Prerelease Info

Bugs

Unused Graphics Gesundheit.

Unused Content in Stages

Title Screen Cloud Manipulation

On the title screen, hold A then press Up, Down, Down, Down, Down, Up, and you should hear a ring sound. From here, you can use the second controller to manipulate the clouds in the background including their angle and perspective with the following controls:

• Up/Down: alter perspective
• Left/Right: raise and lower
• A/C: rotate left or right
• B: speed up speed

Level Select

Press Up, Down, Down, Left, Right, B at the title screen. Note that you will be taken back to the title screen upon completion of the selected level or upon attempting time travel. If the level was ended by attempted time travel, entering the Level Select again and choosing another level will start the level as if you had traveled through time, keeping any rings and accumulated time from the last level.

The level select screen skips from level 1 to level 3. Level 2 was also missing in the PC version, known as R2 because of the way the PC version stored the levels in R# folders. For a specific version of the level: A is the Present version, B is the Past, C is the Good Future, and D is the Bad Future.

Sonic CD Staff's Time Attack Scores

Press Right, Right, Up, Up, Down, C at the title screen to see the best times that the team behind Sonic CD got in Time Attack mode for each stage and act. High-Speed Shoes music plays in the background. Possible developers and their common nicknames are as follows:

CXX: Masato Nishimura (CXXMAJIN)

TOT: Yasushi Yamaguchi (Judy Totoya)

3PE: Masahiro Sanpei (3pei)

ANN: Akira Nishino

KAZ: Kazuyuki Hoshino

DDS: Unknown (Hideaki Kurata?)

TAC: Takumi Miyake

TAK: Takao Miyoshi (Taka Oh)

AXE: Kenichi Ono (AX)

UNT: Unknown (Yuuichirou Yokoyama?)

TNO: Hiroaki Chino (TINON)

Stage 1-1   00'24"10   CXX
Stage 1-2   00'21"55   TOT
Stage 1-3   00'21"08   ANN
Stage 2-1   00'49"60   TOT
Stage 2-2   00'47"50   TOT
Stage 2-3   00'14"85   SPE
Stage 3-1   00'41"20   SPE
Stage 3-2   00'54"75   SPE
Stage 3-3   01'01"33   KAZ
Stage 4-1   00'28"85   ANN
Stage 4-2   00'36"25   DOS
Stage 4-3   00'59"60   DOS
Stage 5-1   00'50"10   TAC
Stage 5-2   00'48"83   AXE
Stage 5-3   01'10"50   DOS
Stage 6-1   00'33"65   CXX
Stage 6-2   00'27"96   TAX
Stage 6-3   01'09"75   SPE
Stage 7-1   00'32"78   ANN
Stage 7-2   02'08"41   UNT
Stage 7-3   01'30"75   TNO
Special 1   00'17"00   CXX
Special 2   00'14"85   TOT
Special 3   00'16"00   CXX
Special 4   00'20"65   KAZ
Special 5   00'22"35   KAZ
Special 6   00'16"95   CXX
Special 7   00'19"20   KAZ

Sound Test/Debug Mode

At the title screen, press Down, Down, Down, Left, Right, A to go to the sound test. By entering the following codes, you can get the corresponding image, debug mode, and/or extra after pressing Start.

Image	Code	Description
	FM NO.40 PCM NO.12 DA NO.11	Tails holding goggles next to a fourth-generation Lotus Seven, with the words "SEE YOU NEXT GAME" above it. This code also activates the debug mode: like the previous Sonic games, press B to change from Sonic to an object, A to cycle through objects, and C to place an object on the screen. Drawn by Yasushi Yamaguchi (also known as Judy Totoya, as seen here), character designer for Tails, and special stage designer for Sonic CD. The "Little Planet" theme plays here. The Tails unlock screen on the 2011 remake and on the version used in Sonic Origins also says "SEE YOU NEXT GAME", likely as a reference to this screen. Here, the music uses Quartz Quadrant Good Future.
	FM NO.42 PCM NO.04 DA NO.21	An unusual Batman tribute. Drawn by Takumi Miyake, landscape and visual designer for Sonic CD. The final boss music plays in the background.
	FM NO.42 PCM NO.03 DA NO.01	Sonic, Metal Sonic, and Eggman gettin' funky. Drawn by Kazuyuki Hoshino, character/special stage/visual designer, and illustrator for Sonic CD. Metallic Madness Present music plays in the background.
	FM NO.44 PCM NO.11 DA NO.09	A cute Sonic with grey eyes. The Palmtree Panic Good Future music plays here. The message says "ゆーあーくーる　by さんちゃんず" (You are cool, by Sanchanzu). Drawn by Masahiro Sanpei, landscape designer and animation visual director for Sonic CD.
	FM NO.46 PCM NO.12 DA NO.25	A rather creepy wallpaper collage featuring multiple Sonics with freakish humanoid faces. The boss music plays. The Japanese text reads "たのしさ∞　セガ・エンタープライゼス　まぢん画" (Infinite fun. Sega Enterprises. –Mazin Picture). Drawn by Masato Nishimura, landscape designer for Sonic CD. Mazin/Majin is his childhood nickname, as explained here - although the spelling "Majin" is used in Dark Wizard to refer to Masato Nishimura, it has been officially confirmed that the easter egg itself is spelled Mazin. たのしさ∞ (Infinite fun) is a phrase that was written on Sega Sougou catalogues. At one point, a button command would have changed "たのしさ∞" (Infinite fun) to "楽しさあまって憎さ∞" (Infinite hatred proceeds from excessive fun), a phrase derived from "可愛さ余って憎さ百倍" (The greatest hate proceeds from the greatest love) but it was deleted from the game for unknown reasons. Contrary to popular belief, and even SEGA's own description for the mobile release, this is not an anti-piracy screen in any version of the game. Despite its creepiness, Nishimura has stated it was not intended to frighten the player, with the creepiness being owed to the unsettling U.S. boss theme. (Source: https://twitter.com/Mazin__/status/72095722316632064)
	FM NO.07 PCM NO.07 DA NO.07	The text "WELCOME TO SECRET SPECIAL STAGE" will appear, after which that stage will load (see here).

Unused Objects

Sprite	Name	Description
	Broken Switch	A broken switch that may have been used in the Bad Future of a Zone to prevent access to certain routes. Regular switch sprite present for comparison.

(Source: Sonic Retro)

Unused Monitors

There are some monitors that aren't used in the final game but are used in some of the prototypes. The player can access the monitors in all major releases of the game from the Debug Mode. The S and Clock monitors can also be used in Palmtree Panic Act 3, using debug to place Sonic in a secret room located underneath the boss arena.

Sprite	Name	Description
	Clock Monitor	This monitor is supposed to stop time for a few seconds, but it doesn't work correctly. It can stop the animations of rings and monitors as well as rotating palettes, but that's it. It also disables the bouncy floor in Wacky Workbench.
	Combine Ring Monitor	This monitor has no effect. In the v0.02 and 510 prototypes, it had the same effect as the "S" monitor, while in the v0.51 and 712 prototypes it acted as an invisible shield that can stack with a regular shield. According to concept art found in Sonic Origins, this was intended to be used for the Combine Ring, a powerup that would wound up unused in the final game and reserved for Knuckles' Chaotix, where this asset would be reused. An updated variant in the form of the Hyper ring being used in Sonic Mania. The flag that gets set when this monitor is destroyed is internally called "conbine_ring", according to the Gems Collection symbol data, further supporting the fact of the original intention of this monitor.
	"S" Monitor	Breaking this monitor gives Sonic invincibility, power sneakers, and a shield all at the same time. The icon originates from but also goes unused in Sonic 1. According to a former Sega Europe QA tester, these monitors replaced the ring monitors in every Zone once the player completed the eighth Special Stage, which contained an additional Time Stone at one point.

Unused Sounds

Time Warp

This sound effect is odd in that it's a CD audio track on the disc. When the game disc is inserted into a CD player, one can hear this sound on track #2, with iTunes and other CD players labelling the track as "Metal Sonic". The v0.51 and 712 prototypes used this sound for time travel.

Other Sounds

Sound ID	Sound	Description
FM NO.21		Not sure what it is. Sounds like it would come from a harmonica? FM NO.22 is a duplicate of this sound.
FM NO.26		Sounds like a Spin Dash or a Super Peel-out being jammed.
FM NO.48		A different version of the sound heard when pressing a button.
FM NO.49		The warning bell usually heard underwater in other Sonic games, only high-pitched. The 2011 rerelease uses this sound, albeit at a lower pitch, and later used in Sonic Origins.
FM NO.50		Sounds like something being shot.
FM NO.54		An electrical sound of sorts.
FM NO.55		A loud, harsh buzzing sound.
FM NO.60		Not sure, but it sounds like something rising or powering up.
FM NO.61		This sounds like FM NO.55, but it has a resonating sound underneath it.
FM NO.63		An echo-y spike-like sound.
FM NO.66		A very high-pitched "ding" sound. Possibly intended for the unused Combine Ring powerup, as this sound effect was later used in Sonic Mania when obtaining the Hyper Ring powerup.
FM NO.67		A higher-pitched version of Sonic losing his rings. This might've been intended for use when Sonic gets hurt while shrunken down in Metallic Madness.
FM NO.68		This one sounds like FM NO.63, only without an echo.
FM NO.69		This one sounds similar to the door sound at the end of the Metal Sonic race.
FM NO.75		This sounds like variant of FM NO.68. Perhaps it could have played alongside the sound.
FM NO.76		Another variant of FM NO.68.
FM NO.77		Yet another variant of FM NO.68.
FM NO.78		You guessed it. Another FM NO.68 variant.
PCM NO.02		Sonic saying "Alright!". The voice actor of Sonic, Masato Nishimura, recalls that it may have been intended to play after passing the goal post at the end of a stage.
PCM NO.05		Sonic saying "Yeah!". This was used as the extra life sound in the v0.51 and 712 prototypes, in the final game he says "Yes!" instead.

(Source: https://twitter.com/Mazin__/status/598087283175108609)

"Comin' Soon" Screen

This screen, which features a scrolling banner saying "COMIN' SOON" while playing the invincibility theme, was used as far back as the v0.02 prototype when only two levels in the prototype were accessible and used for subsequent prototypes after clearing certain Rounds. It managed to survive all the way into the final game and can be viewed by selecting "COMMING" in the Level Select.

Backup RAM Error Messages

There are a few error messages that can show up if there's a problem with Backup RAM that would prevent saving from properly functioning. The game will only allow you to continue without saving if Backup RAM is full. Otherwise, it'll freeze at the error screen if there's corrupted or uninitialized RAM data.

Oddly, the English version of the Corrupted RAM message has broken grammar, like it was written by a Japanese developer. (The other messages also have this Engrish-like quality, but it's less noticeable.) Dr. Robotnik is also mistranslated as "Robotonic", as the Japanese spelling "ロボトニック" is ambiguous and can be romanized in multiple ways. This also happened in Sonic the Fighters.

The "Internal RAM Uninitialized" message is the only one to have been changed in the US version, where it was touched up over the EU version. This change, however, added another weird mistake-- the letters of the word "control" and the letter P in "panel" are shifted up and don't match the height of the other letters on the line. This doesn't happen in the European version, or any other message.

Corrupted RAM

Japan	US/Europe

Internal RAM Uninitialized

Japan	US	Europe

RAM Cartridge Uninitialized

Japan	US/Europe

RAM Full

Japan	US/Europe

Leftover Level Layouts

As a result of the game being built off Sonic 1's codebase, each stage file contains unused copies of the level layouts from Green Hill Zone Acts 2 and 3. The exception to this is level R11A (Palmtree Panic Zone 1 Present), which has some optimizations not applied to the rest of the stage files, including the removal of these unused layouts.

(Source: Devon)

Regional Differences

Almost the entire soundtrack was redone for the American version by Spencer Nilsen because Sega of America thought the soundtrack of the Japanese and European versions sounded too close to the electronic dance soundtracks being produced at the time, so the American soundtrack has more of a rock feel. One example of this is the theme song: instead of "You Can Do Anything", the American version has "Sonic Boom". The only songs that weren't altered were the Past themes since those were played through the PCM chip and not Redbook.

(Source: Sonic Retro)

In addition, there are a few other differences in the American version compared to the original Japanese and European games:

Japan	US	Europe

• The copyright text at the title screen was altered slightly.
• Some of the music placement was switched around. For example, the "Little Planet" theme now plays on the Time Attack screen (rendering the title theme copy only playable in the "Visual Mode" menu), and the music played during the Metal Sonic race is now the normal mix of Stardust Speedway's current Future and not always the "B" Mix.
• In the Japanese and European versions, the player can restart the stage by pausing and pressing all three of the face buttons at the same time. In the American version, only one button has to be pressed. This is at the cost of one life.
• In order to remove Engrish, "YOU ARE GREATEST PLAYER" was changed to "YOU ARE THE GREATEST PLAYER".
• The font used in the end credits' large text was altered, and most credits related to the original soundtrack was removed/replaced.
  • There are no longer sound effects at the beginning of the ending. Due to the extended "Special Edition for North America" credits, the ending theme plays over the entire video and mutes other audio (including the post-credits).
• The bad ending's "TRY AGAIN AND FREE LITTLE PLANET FOREVER" text was shortened to simply "TRY AGAIN".

All of these changes are applied to all regional versions of the PC version, though the 2011 re-release reverts the Metal Sonic racing theme so it always plays Stardust Speedway "B" Mix and mostly restores the original ending videos' exclusive audio when played with the Japanese soundtrack.