Sonic the Hedgehog 3
|Sonic the Hedgehog 3|
Also known as: Baramdori Sonic 3 (KR)
This game has unused animations.
This game has a prototype article
This game has a bugs page
This game has a prerelease article
Sonic the Hedgehog 3 is the third game in the 16-bit Sonic trilogy and the first game with the easily-tricked-by-Eggman redheaded echidna, Knuckles. Originally one big game, Sonic 3 was split into two games due to time constraints and cartridge costs; the second half of the story is its direct sequel, Sonic & Knuckles.
- 1 Sub-Pages
- 2 Level Select/Debug Mode
- 3 Unused Zone
- 4 Sonic 2 Menu Leftovers
- 5 Eighth Special Stage
- 6 Water Levels in Launch Base Zone Act 1
- 7 Hydrocity Dominos
- 8 Unused Objects
- 8.1 Red Revolving Spheres
- 8.2 Unused Foreground Tree Sprite
- 8.3 Breakable Wall
- 8.4 Carnival Night Button
- 8.5 Carnival Night Ring Object
- 8.6 IceCap Breakable Block
- 8.7 Competition Mode Spikes
- 8.8 Unused Elevator
- 8.9 Rotating Platform
- 8.10 Spinning Structure
- 8.11 Grabbable Platform
- 8.12 Leftover Lava Damage Object
- 8.13 Up and Down Spring
- 8.14 Big Sonic on the Sega Screen (Sonic 2)
- 8.15 Shield Object
- 8.16 Other Unused Objects
- 8.17 Unused S&K Mapping Data
- 9 Unused Surfboard Intro
- 10 Unused Sprites
- 11 Unused Level Chunks
- 12 Unused Audio
- 13 Unused Palettes
- 14 Scrolling Credits
- 15 Unused Areas
- 16 Oddities
- 17 Changes in Sonic 3 & Knuckles
- 18 Regional Differences
| Sonic & Knuckles Leftovers|
All sorts of leftovers from the game still in development.
Level Select/Debug Mode
To access a level select and debug mode, press Up, Up, Down, Down, Up, Up, Up, Up after the SEGA logo screen fades to black and Sonic begins to move, but before the title screen appears (about 4.31 seconds after boot). You only have about 1.3 seconds to enter it, and due to this screen having an absolutely ridiculous number of lag frames, it may not always work; you'll hear the ring collection sound if you did it right. Alternatively, you can unlock the level select by these alternate methods:
- You can access the leftover Sonic 2 Options menu (see below) and enter the Sonic 2 level select code in the sound test (19, 65, 09, 17).
- You can also use Game Genie code AA6T-AAXC or Pro Action Replay code FFFFD0:0100 to access the level select.
- If you are playing on a real Mega Drive/Genesis console and don't mind risking the long-term health of your console and cartridges, then another method is to load up Sonic 2, unlock its level select (19, 65, 09, 17 in the sound test), swap the cartridge with Sonic 3 without turning the power off, and then press Reset. This works because the RAM variable that unlocks the level select is preserved when you reset the console (Sonic 3 was built upon the Sonic 2 source code, and thus shares a number of RAM variables).
To find the level select on the title screen, simply press Up to reveal "SOUND TEST" and press Start. To activate debug mode, select a file/level, hold A and press Start, and keep holding A until the level begins. You can also hold C and press Start to highlight high-priority background tiles (tiles that overlap Sonic and other sprites).
While in debug mode, you have access to the following:
- Infinite time
- Debug coordinates (in place of score)
- Sprite counter (in place of time)
- Placement mode: Press B to enter placement mode, which allows you to move Sonic anywhere in the level with the D-Pad and place objects from a predefined list (not all objects may be available in a given level). In this mode:
- Press A to move forward one object.
- Hold A and press C to move backward one object.
- Press C to place the object.
- Press B again to return to normal gameplay.
- Character animation viewer: hold C and press B to rapidly cycle through all available animation frames for the current character (pause the game and use frame advance to view individual frames). Press B again to return to normal gameplay.
- Pause options:
- Press A to go back to the level select.
- Hold B to progress the game in slow motion.
- Press C to advance one frame.
If you die, press B to enter placement mode, and then press B at a safe spot to revive yourself. However, trying to place an object in this death state will freeze the game. Additionally, do not enter debug mode at any point where Sonic's sprite rotates (such as while standing on the red-and-white cylinders in Carnival Night Zone) or the game will crash.
The level select menu shows what the level order was at one point. The Sonic 3 Zones are in their normal order, but Flying Battery from Sonic & Knuckles is listed between Carnival Night and IceCap. Following Launch Base are Mushroom Valley (an early name for Mushroom Hill) and Sandopolis, but neither of those can be selected. The Sonic & Knuckles bonus stages are also listed in the level select but none of them can be selected.
According to commentary from the Sonic Jam strategy guide, IceCap was meant to follow Flying Battery as Sonic was supposed to break down the door at the end of the latter Zone and use it as a snowboard. There's also a variety of unused songs, all from Sonic & Knuckles, in the sound test.
Furthermore, all the graphics here (including the level icons) are recycled from Sonic the Hedgehog 2, and the icons are shown in the Sonic 2 order, such as Emerald Hill's icon for Angel Island and Casino Night's icon for Carnival Night. Interestingly, the second "2P VS" entry shows the unused Hidden Palace icon.
Zone ID $0D is unused, but appears to be empty. It tries to load some resources from the end credits. Act 2 of this Zone was later used for the credits in Sonic 3 & Knuckles. Attempting to load this zone will usually crash the game, and if you manage to get out of it, it causes some very strange bugs causing the game to act very strangely.
It is believed this zone was originally meant to be a 2P VS zone for multiple reasons:
- It is internally next to all used 2P zones.
- In the November 3rd prototype and Windows port, there is an unused track (often incorrectly referred to as an unused Super Sonic theme) that could be situated for a 2P zone.
- There are six 2P zones listed in the level select. The 6th zone listing simply points to the Gumball Machine bonus stage, however.
Sonic 2 Menu Leftovers
By setting the game's screen mode to $24, you can access the Sonic 2 options menu in Sonic 3! Alternatively, you can use the patch code FFF600:2400 or hack the menu back in yourself.
As all the options here are selectable normally through other means in Sonic 3, the only real benefit of this is entering the Sonic 2 level select code to access it in Sonic 3.
It's also possible to find the 2 Player Level Select from Sonic 2 using the patch code FFF600:1C00. However, selecting any of the zones on this screen will send you back to the title screen, so you can't really do anything with this menu. Data for the Sonic 2 Results Menu also exists, but it can't be seen.
Eighth Special Stage
There is an eighth Special Stage with a grey Chaos Emerald (much like the fifth Emerald) that is inaccessible during normal gameplay. To access it, open the level select, set the sound test selection to 07, then hold A and press Start on "Special Stage 2".
The stage is fully playable, although it may occasionally slow to a crawl when collecting a blue sphere, which may have contributed to its removal. The Emerald has no special effect in-game, and does not appear on the end-of-stage tally in any form other than a score increase. The complete lack of rings also makes it impossible to get a Perfect Bonus on this stage.
Sonic Mania would reuse this layout for a Bonus Stage, replacing some of the blue spheres with rings to allow a Perfect Bonus.
Water Levels in Launch Base Zone Act 1
There are 5 areas containing water in Launch Base Zone Act 1 that either raise or lower the water level in some specific areas. From this, it's not unreasonable to assume both Acts of LBZ would contain water .
To view these levels, add the patch code FFF730:0100 and change VDP 0x04 to 0x14. The water levels can be seen in the ROM at address 0x5350.
The first level can be seen in the ROM address at 0x51EE and should increase the water level to 0A80, but doesn't due to an error.
The fifth level is located from 0AC8 to FFFF and makes the water disappear.
These domino/die-like tiles are used as placeholder graphics for the animated orbs in Hydrocity's background columns. They can be seen in-game if the animated graphics are prevented from loading somehow:
Red Revolving Spheres
A spinning mass of red spheres, which can be placed in the first half of Angel Island Act 1 via debug mode. The spheres resemble those that appear in the game's special stages, but the object itself seems to have no apparent gameplay purpose. When it is placed, many palette and VRAM complications occur in the level, and the game slows down considerably. The object can be manipulated with the second controller.
- Up - Rotates the object vertically.
- Right - Rotates the object horizontally.
- Down/Left - Moves the object up or down.
- A/C - Changes the object's size.
- B - Rotates the object sideways.
- Start - Toggles automatic rotation.
The Nov 3, 1993 prototype reveals, however, that they're leftover from a tech demo that served to test the 3D mechanics of the Special Stages. It's worth noting the object is not identical to one seen in the test stage.
Unused Foreground Tree Sprite
Despite its similar appearance to the trees seen at the end of Angel Island Zone Act 2 when Robotnik flies through the forest, this is actually a separate object entirely that goes completely unused. It's meant to be placed in the foreground, and its graphics are located with the unused switch graphics, suggesting it may have been used earlier in development. It can be placed with debug mode.
A breakable wall, placeable in Angel Island Act 2 using debug mode. It comes in two variations: one that acts as a wall obstacle that can be destroyed with the Spin Dash, and one that acts as a door that opens with a switch.
Carnival Night Button
A button of unknown purpose. It can be placed in either Act of Carnival Night Zone via debug mode, but it doesn't appear to do anything. Also unused in Sonic 3 & Knuckles. Knuckles (Sonic/Tails' story) pushes a button like it in Act 2 to darken the place.
Carnival Night Ring Object
An unknown object that appears to spawn slope collision when placed.
IceCap Breakable Block
A glowing block that can be placed in either Act of IceCap Zone via debug mode. Jumping on it destroys it like the ice blocks. Also unused in Sonic 3 & Knuckles.
Competition Mode Spikes
A set of spikes for Competition Mode. Spikes do not appear in any of the five courses, but they can be placed with debug mode.
An unused elevator object defined as object ID 12. The graphics no longer exist, but the leftover symbol name of elev06 in Sonic & Knuckles Collection seems to indicate it was intended for Launch Base Zone, possibly before the new elevators were created. It can be operated using a switch.
A kind of spinning platform-like object with undefined graphics, with object ID 1A. When touched, it locks the player to the center of the object; the faster the player runs, the further they're thrown after exiting it. However, this behavior is likely an unintended side effect of a bug in the object's code. If the bug is fixed, it behaves more logically like a standard rotational obstacle. The rotation of the object can be manipulated using the second controller. It was labeled as rollita in Sonic & Knuckles Collection's symbol data. This object may also have been created for Launch Base Zone.
A curious object that damages the player if hit from above, but swings from side to side if hit from below. Its graphics have not been found, and its animation resembles something turning. Identified as Object 1C. It may also have been created for Launch Base Zone.
A normal platform with a grabbable bottom. The bottom portion of the graphics are corrupted, but it seems to fit Launch Base Zone the best. Its ID is 1D.
Leftover Lava Damage Object
This object was used in Sonic 1 and Sonic 2 to damage the player when they touch lava, but doesn't work here. It's possible to change the size of the area by modifying its variable. ID 27.
Up and Down Spring
Intended for Flying Battery Zone, this object creates a spring that goes up and down temporarily. It also bounces the player abnormally high. Identified as ID 3D.
Big Sonic on the Sega Screen (Sonic 2)
There is leftover code from the large Sonic on the Sega screen in Sonic 2. The object seems to be a fairly old leftover as it is still using the old Sonic 2 object format. The sprite mappings still exist.
Code for a fourth type of shield exists inside of the ROM. The shield itself is the ordinary non-elemental shield as seen in Sonic 1 and Sonic 2. It is unknown whether or not this is simply a leftover, or if it was originally planned for the game. It is worth noting that the shield sound from Sonic 2 remains unused in the sound test. Interestingly, it exists under three valid monitor shield subtypes: 00, 02 and 03.
You can activate this shield type manually by changing RAM address FFB02B:00 to 01.
Other Unused Objects
Objects 8F-98 delete themselves when loaded, which is rather unusual. One of these objects is used in the Mushroom Valley object layout, suggesting that they were once objects that belonged to the Sonic & Knuckles Zones. Objects 6F-7F are represented as rings in Sonic 3 and were apparently removed manually, but in Sonic 3C (prototype 0408), these IDs belong to objects from Flying Battery Zone. Object 84 is another unused and removed object; according to the November 3rd Prototype, this object was an early version of Hey Ho, the Mushroom Valley/Hill Act 1 boss.
Unused S&K Mapping Data
In Sonic 3 there remains some leftover sprite mapping data for Sonic & Knuckles objects, largely consisting of badniks that would have appeared in the Sonic & Knuckles zones.
Unused Surfboard Intro
Sprites for an alternate intro sequence in which Sonic surfs onto Angel Island, rather than riding in on the Tornado. Interestingly, Sonic looks like his Sonic 2 incarnation, making this a fairly old leftover. This intro is used in the November 3, 1993 prototype. In the final, the surfing Sonic sprite can still be placed in Angel Island Zone 1 via debug mode.
The sprites used when Sonic ditches the surfboard.
|An item monitor displaying static that harms you when broken, change a monitor to subtype 00 to view the static monitor. Used in Angel Island in the November 3rd prototype.|
|A monitor that can transform Sonic into Super Sonic and Tails into Glitched "Super Tails" without needing to collect Chaos Emeralds. This monitor is present in Debug mode only.|
|Sonic in his signature "waiting" pose, but instead of pointing towards the direction he's facing, he falls asleep from boredom. Interestingly, this animation was used in the Game.com version of Sonic Jam, as well as Sonic X for the Leapster.|
|Sonic whistling. This was also used in the Game.com Sonic Jam.|
|A black & white version of Sonic's death sprite, similar to the one seen in the previous two games. It's still not used.|
|This would be used for Flying Battery Zone's monkey bars in Sonic & Knuckles and Tails' sprites will be used in Sonic 3 and Knuckles. Sonic's sprites seem to match up better with his Sonic 2 sprites than his Sonic 3 ones, which wasn't fixed in Sonic & Knuckles.|
|This would be used for the intro cutscene of Mushroom Hill Zone Act 2 in Sonic & Knuckles.|
|This would be used in Sonic & Knuckles when grabbing the swinging poles in Mushroom Hill Zone.|
|This would be used in Sandopolis Zone in Sonic & Knuckles when scaling down the towers.|
|Leftover continue icons from Sonic 2. These are still mapped to the original palette.|
|A leftover animation from the Sonic 2 continue screen.|
|Knuckles' life icon which would later see use in Sonic & Knuckles.|
|Knuckles text which would have been used upon Act and Special Stage completion. It can be seen in-game by making a save file with Knuckles as your character.|
|Unused Knuckles sprite for the continue screen.|
|Unused Knuckles sprite from the data select screen. It was later used in Sonic 3 & Knuckles. It can be seen via the way listed above.|
|Unused gliding, climbing and falling frames for Knuckles in 2-Player mode, despite him not having these abilities there (he uses Sonic's Insta-Shield ability, much like his single-player "slot" uses Sonic). The recombined game, Sonic 3 & Knuckles, does not restore these functions (assuming they were ever implemented).|
|A set of sprites where Eggman has a panicked facial expression. One of these sprites shows him attempting to jump. Sonic & Knuckles didn't use them either.|
|This was used for the Flying Battery laser boss. It was later used in Sonic & Knuckles.|
Appears to be nothing more than Eggman flying away towards the horizon. This is actually another object with coding left in the game, but it's never called by any routine. The animation somewhat fits with the way the Death Egg falls at the ending cutscene after the Big Arms fight and would've teased the second part of the game, however, the Death Egg noticeably falls on the opposite direction of where Eggman goes in the actual game, it was probably originally meant to be falling from the left side instead. This can be re-enabled using the PAR code 05165A:04F2.
|Dr. Robotnik poses intended for the unused Flying Battery Zone Act 2 boss and would later appear in the lock-on game, however, the left-most sprite also goes unused even during the actual boss fight due to a coding error, and it was meant to appear when the Hang Mobile started swinging up and down, this was not fixed in Sonic & Knuckles.|
|A smaller rendition of the Death Egg that seems to be part of a Death Egg hologram projector, which itself is unused in Sonic & Knuckles.|
|Diagonal frames of the Penguinator badnik from IceCap Zone. These can be seen for a split-second if you place a Penguinator on the large hill at the beginning of Act 1 using debug mode.|
|A save file icon for Flying Battery Zone before it was re-ordered to be in Sonic & Knuckles, which is different than the corresponding icon in Sonic 3 & Knuckles, displaying the interior part of the stage rather than the exterior. It resembles a part of the beginning section of the zone from the November 3rd Prototype. You can view this icon in the PC and Genesis versions by hacking the save data to access level slot $04, or by using PAR codes 00C324:601E + 00C338:6002 to view it in a completed game save slot while scrolling through the zones.
(Source: Sonic Retro)
|Unused sprites from IceCap Zone Act 1. While the teleporter pad ended up being used in Sonic 3 & Knuckles for Knuckles' transition into the stage, the unusually oversized ice boulder which actually fits in some of the cave's halls was never used.|
|An unused S gumball intended for the Gumball Machine bonus stage. It can also be seen hidden among the other balls at the bottom of the machine. Its programming is undefined, though a possibly useless ID of 08 might have been created for this gumball, if the S and the palette cycle which is nearly the same one used on Super Sonic is any indication, it might have been related to it. It's also unused in Sonic & Knuckles. It does, however, set an unrelated RAM address to 07.|
|Located far in the back of the gumball machine, obscured by the other gumballs and the glare of the glass, sits a blue gumball. The shade of blue seen here varies from the bubble shield gumball.|
|A sprite resembling a metallic structure that, based on its location at offset 18DB46, would have been used during the fight against Robotnik in Angel Island Zone Act 2. The assembly and color palettes may be wrong.|
|Leftover sprites from early versions of the game that had a progress bar in Competition mode. These sprites can be seen in the Nov 3, 1993 prototype.|
|Unused lap counter digits. These sprites can be seen in the Nov 3, 1993 prototype, as the lap number has no cap, but they use an older style.|
|This is an unused font, located directly after the font for the timer in the competition mode. It's very likely that it was used earlier in development.|
|This graphic that looks vaguely like a clock or medal, was located in the data for the font above. The palette is unknown.|
|A set of sprites resembling a shadow found within the graphics used for the Tornado. It would have likely appeared under the Tornado during the opening intro.|
|During the boss fight at the end of Marble Garden Act 2, Robotnik will fly towards the horizon before initiating his next attack. This effect uses a sprite software scaling algorithm that allows this to be achieved. However, the effect begins taking place before Robotnik flies completely onscreen and as a result, the full unscaled sprite is never seen.|
|These sprites are used in Knuckles' unused Marble Garden Act 2 boss battle.|
|This sprite is used in the Launch Base Zone Act 2 laser boss battle, but it is obscured and cannot be seen.|
|While these graphics are used in Sonic & Knuckles, they appear in this game in a mangled form on Knuckles' unused, broken post-Launch Base Zone Act 2 boss cutscene.|
|These do appear in mangled form in Knuckles' unused, broken post-Launch Base Zone Act 2 boss cutscene.
These graphics were later used in three Sonic 3 limited edition/Sonic & Knuckles prototypes; Sonic 3C 0408, Sonic 3C 0517, and Sonic & Knuckles 0525 respectively. This was a bomb shoot that Eggrobo used to drop the bomb on Knuckles. Oddly, it is not used in the final game, but it might have something to do with Big Arm's graphics loading over the graphics of the bomb shoot (Knuckles originally did not fight Big Arms).
|The Blaster badnik from Flying Battery Zone still has its sprites and object code leftover in Sonic 3. The palette used here is from IceCap Zone because Flying Battery's true palette no longer exists.|
|The Technosqueek badnik from Flying Battery Zone also has its sprites and object code leftover in Sonic 3.|
|Owing to its late removal, many assets related to Flying Battery's bosses are still in the ROM, but unused. This is used for the Gapsule miniboss in Sonic & Knuckles, but with minor palette differences. The boss itself still exists and can be fought by hacking the game to load Flying Battery Zone Act 1.|
|The laser turret in Flying Battery Zone Act 2's mid-boss, the laser barriers on either side of the arena and Eggman's control panel all still exist and are fully functional, later appeared in Sonic & Knuckles, of course...|
|The Hang Mobile is here too.|
|This light bulb is used in Carnival Night Zone, but it has an unused function; if the water rises over it, it will explode and show the unused frame seen on the right. This can never be seen because the light bulbs never make contact with the water in the actual game.|
|Palette and graphics data for the gold player-bouncing spheres that are present in the Sonic & Knuckles special stages exist in Sonic 3. The palette is loaded every time the player enters the special stage, but none of these spheres ever appear, their coding is also non-existent in the game.|
Unused Competition Mode Title Cards
Unused title cards exist for Competition Mode and are fully programmed, but disabled. They can be re-enabled using the following patch codes:
|02CA90:6030||Enable 2P zone title cards|
|02CACA:FE10||Pick title card by Current_zone|
|02CB42:004D||Set art_tile instead of render_flags|
|02CB44:000B||Set art_tile instead of render_flags|
When the title cards are enabled, VRAM issues with the level graphics occur, which may have contributed to their removal. Interestingly, the title cards are still using the old level order where Desert Palace Zone precedes Chrome Gadget Zone. This was changed in the final so that the zone names used alphabetical order.
Unused Super Sonic Frame
Super Sonic has an extra idle frame and extra colors in his palette cycle that end up going unused. The unused frame makes the animation a bit smoother than what is actually seen. The unused colors are due to an oversight in one line of code, it mistakenly skips the last six frames ($36 instead of $3C).
Oddly, the smoother colors don't happen with underwater palettes, suggesting it was scrapped early.
While not technically unused, only the bottom of the ship appears in normal gameplay.
Act Clear Signs
In Sonic 3, the sign frames are uncompressed and loaded dynamically over each other to conserve video memory. This said, also present in the game's data is an unused copy of the same art compressed like in Sonic 2, strongly suggesting it is from earlier in development.
Although Sonic, Tails, and Robotnik are basically the same as their Sonic 2 counterparts, Knuckles appears for the first time, with a slightly different appearance relative to the final art. This early version is still present in Sonic & Knuckles.
Hidden Placeholder Tiles
Various numbers and letters are loaded in and replaced with animated stage tiles. Curiously, they differ between zones, and some are written in Japanese characters.
Out of Bounds Backgrounds
Chrome Gadget Zone has a large portion of its background hidden by the stage and palette.
Unused Level Chunks
Several chunks of levels are unused during the game. The chunks are placed starting at address FF8088, and can be inserted into levels by entering the given values into FF8088:XX. Most of them have no noticeable differences from used chunks.
Angel Island Zone
Marble Garden Zone
Carnival Night Zone
Acts 1 and 2:
Acts 1 and 2:
Launch Base Zone
Acts 1 and 2:
24, This chunk was used in the Act 1 Bossroom in the November 3rd 1993 Prototype. It would have been used with chunk 23, which was later changed into a generic ceiling chunk, and it would warp you up to the top of the bossroom allowing you to reach two separate platforms in which you could hit the boss.
Most of the music from Sonic & Knuckles can be played from the Level Select/Sound Test.
|$09||Flying Battery Zone Act 1. The loop point in the "echo" track of the lead instrument is set slightly later than the rest of the tracks; as a result, it falls further and further out of sync every time the song loops. This was fixed in Sonic & Knuckles and its lock-on.|
|$0A||Flying Battery Zone Act 2.|
|$0F||Mushroom Valley/Hill Zone Act 1.|
|$10||Mushroom Valley/Hill Zone Act 2.|
|$11||Sandopolis Zone Act 1.|
|$12||Sandopolis Zone Act 2.|
|$13||Lava Reef Zone Act 1.|
|$14||Lava Reef Zone Act 2/Hidden Palace Zone.|
|$15||Sky Sanctuary Zone.|
|$16||Death Egg Zone Act 1. For some odd reason, this plays in Sky Sanctuary Act 2 in Sonic 3 alone.|
|$17||Death Egg Zone Act 2. Death Egg Zone uses this for acts 1 & 2 in Sonic 3 alone.|
|$18||Sonic & Knuckles Act 1 Boss. This can be heard while fighting any Hydrocity Zone boss if you jump out of the water after the drowning music starts.|
|$1A||The Doomsday Zone.|
|$1B||Glowing Spheres Bonus Stage.|
|$1D||Slot Machine Bonus Stage. Oddly, the unused Glowing Spheres Bonus Stage in Sonic 3 alone uses this music.|
Many of these sound effects would see use in Sonic & Knuckles, though some of these sounds would also be unused there.
|$3A||This is a shield sound leftover from Sonic the Hedgehog 2.|
|$40||Unused; sounds like an electric zap. This sound would later be used for the Thunder Shield in Sonic Generations and Sonic Lost World, suggesting that it may have been an early sound effect for the Thunder Shield. The Phantom Egg also uses this sound for its barrier in Sonic Mania.|
|$53||Laser charging sound, used for the Flying Battery Zone laser boss and the jumping spike balls in Lava Reef Zone Act 2.|
|$54||Laser firing sound, used for the Flying Battery Zone laser boss.|
|$55||Sound effect used when a brick in Sandopolis Zone goes across a line of black rotating circles.|
|$5A||Unused; sounds like something revving up. This sound effect would see use in Sonic 3D Blast.|
|$5C||The sound of Mecha Sonic short-circuiting after it's defeated.|
|$69||The sound that plays when you push a brick in Sandopolis Zone.|
|$6B||Unknown, possibly unused; sounds like a higher-pitched version of the sound heard when hitting an R, Up or Down block in the Special Stage from Sonic 1.|
|$6D||Unused; sounds like a door closing.|
|$71||Duplicate of $3A; another shield sound leftover from Sonic the Hedgehog 2.|
|$7A||The sound of the Lava Reef Act 2 boss emerging from lava.|
|$7C||Used by the magnetized platforms in Flying Battery Zone.|
|$7D||Unused; sounds like mild rattling.|
|$84||Unused; sounds like something charging up. Only seems to be referenced in some zone with a high level ID which is composed of garbage data.|
|$85||Unused; sounds like it would have been used in cooperation with $84.|
|$87||The sound that plays when you bounce on a mushroom in Mushroom Hill Zone.|
|$88||Mushroom Hill Zone elevator sound.|
|$89||Mushroom Hill Zone satellite dish (from Dr. Robotnik's season-changing machine).|
|$8A||The sound the ghosts from Sandopolis Zone make when they vanish.|
|$8B||The sound of the Mushroom Hill miniboss chopping a log.|
|$8C||The sound of the Mushroom Hill miniboss struggling to chop a log.|
|$8D||Unknown, possibly unused; a very quiet sound.|
|$8E||Unused; another electric rev-up sound.|
|$8F||The sound the door on the pyramid in Sandopolis Zone makes when it opens.|
|$90||Door closing sound from Sandopolis Zone, and also the sound of Knuckles hitting the ground after his defeat.|
|$92||Ghost sound effect from Sandopolis Zone.|
|$93||The sound that plays when the armor on Dr. Robotnik's golem machine comes back on. This sound was reused later in Sonic Mania as the sound for the first mini-boss spawning.|
|$95||The sound of the giant hand appearing to attempt to crush you in the Lava Reef miniboss.|
|$96||The sound the giant spikeballs in Lava Reef Zone make when they roll around.|
|$97||The sound a Toxomister makes when it sprays its toxic gases.|
|$98||The sound of a falling stalactite in Lava Reef Zone.|
|$99||Unused; A small "tick" sound.|
|$9A||The sound of the pop-up springs from Sky Sanctuary Zone.|
|$9B||A loud bang that plays when the Sandopolis Zone Act 2 boss comes closer to you.|
|$9C||Sound that plays when a Super Emerald regains its color.|
|$9D||The sound of the missile reticles in the Lava Reef Act 2 boss. This sound effect is also used by the Green Hill Zone Act 2 boss from Sonic Mania.|
|$9E||The sound of a platform breaking upon coming into contact with the Lava Reef Act 2 boss.|
|$A0||The sound of the Lava Reef Act 2 boss firing a missile.|
|$A1||Unused. A low-humming, unsettling sound. This sound effect is used by the Stardust Speedway Act 1 boss in Sonic Mania.|
|$A2||The sound of the speed-up launchers in Flying Battery Zone and Death Egg Zone.|
|$A3||Death Egg Zone lift platform sound effect.|
|$A4||The sound that Mecha Sonic makes when he goes super.|
|$A5||Unused; sounds like something rising or powering up?|
|$A6||Unused; another dashing noise.|
|$AE||The sound that the seesaw mushroom from Mushroom Hill Zone makes when the black weight lands on it. This sound is also used in the Bonus Stages in Sonic & Knuckles.|
|$B5||A leftover from Sonic 1 that was used for the breakable diamonds in the Special Stage. Might have been used for the Slot Machine Bonus Stage which is based off that Special Stage.|
|$BC||Unused? Possible waterfall sound effect.|
|$C2||The sound of the flamethrowers in Flying Battery Zone and Lava Reef Zone.|
|$C4||The sound Red Eye makes when it gets angry.|
|$C5||Unused; sounds like it would be used in coordination with $C4.|
|$CA||The sound of the light beam transportation systems in Death Egg Zone.|
|$CE||The gusts of wind from Mushroom Hill Zone. Also used in Knuckles' ending after Super Mecha Sonic explodes.|
|$CF||A louder version of $CE that might be unused even in Sonic 3 & Knuckles.|
|$D1||Possibly unused; another very faint sound that may sound like static.|
|$D3||Used in Sonic & Knuckles when the Death Egg flies through Sky Sanctuary zone; sounds like a quiet version of $CD.|
|$D4||Used by the bouncing puzzle room in Death Egg Zone.|
|$D5||Used when the lava falls from Lava Reef Zone. Repeatedly pressing the C button when playing this sound in the Sound Test makes it play longer.|
|$D6||Unknown/unused; rumbling/electric sound?|
|$D7||The sound of the elevators in Lava Reef Zone and Death Egg Zone.|
|$D8||Unused; sounds like a screeching warning siren. Repeatedly pressing the C button when playing this sound in the Sound Test makes it play longer. It was used in the November 3th 1993 prototype when Robotnik appeared behind the trees at the end of Angel Island Zone Act 2.|
|$D9||The sound the electromagnets in Flying Battery Zone and the black gravity spheres in Death Egg Zone make.|
|$DA||The sound of the wind trap Knuckles activates in Mushroom Hill Zone.|
|$DC - $DF||All of these sounds are duplicates of $DB (heard when running across water in Hydrocity Zone) and are likely placeholders. Sonic & Knuckles replaces $DC with its credits medley.|
Sonic 2 SEGA Screen:
The color palettes of the Sonic 2 SEGA screen are abandoned in offset 08C134.
Sonic 2 Title Screen:
Sonic and Tails' color palettes from the title screen are located in offset 08C1B4.
Sonic 2 Prototype Level Select:
For some obscure reason, it is still possible to see the color palettes from the level select screen of the Sonic 2 prototypes in offset 08C1D4.
Early Launch Base Zone Act 2 Water:
This color palette set does not include colors for Sonic underwater, which suggests it would be used after some cutscene or scene change in Launch Base Zone. There is little difference in the colors, nothing too important. It closely matches up with the November 3rd 1993 Act 2 water palette. It can be found at offset 08CB14.
|November 3rd 1993 Palette|
Glowing Spheres Bonus Stage:
An old version of the Sonic & Knuckles Bonus Stage color palette can be found in offset 08CDB4. It is exactly the same as the Sonic 3C 0408 and the Sonic 3 November 3rd prototype.
Slot Machine Bonus Stage:
This palette is quite different from the Sonic & Knuckles prototypes, and can be seen in offset 08CE14. It is exactly the same as the Sonic 3 November 3rd Prototype.
Lava Reef Zone cycle 1:
This palette cycle would have been used for animating the Lava, it can be seen if Lava Reef is accessed in Sonic 3. There are no notable differences from the S&K version. It can be found at offset 002EFE.
Lava Reef Zone cycle 2:
This palette cycle would have been used for the dark glowing rocks, and it can be seen if Lava Reef is accessed in Sonic 3. There are no notable differences from the S&K version. It can be found at offset 002F7E.
These palettes can be found at offsets 05275C and 05277C. They are copies of the palettes used in Angel Island Zone Act 2 and IceCap Zone Act 2, respectively.
Unused Knuckles 1-Player palette
The palette that is used for Knuckles in Sonic & Knuckles and this game's lock-on version is abandoned at offset 08C2F6.
The game contains an unused, unfinished scrolling credits routine, which can be activated by setting RAM address FA87 to 2 during the credits sequence. The actual credits were apparently not yet in place when this was abandoned, as it scrolls small and large versions of the letters B-F, and then abruptly fades to the Sonic 3 logo screen. The final staff roll simply fades between static pages of text.
Hydrocity Zone Act 1
The starting corridor from Act 2 is present in the Act 1 layout; even though it gets overwritten and ends up unused.
Carnival Night Zone Act 1
A long unused corridor in Act 1 that starts at coordinate 3400 to 3800 at the high 04AC is very similar to Act 2 when Act 1 is rewritten after the fight against the mini-boss. However, this corridor is at a height above the rewritten area and is never seen.
Carnival Night Zone Act 2
There is a long vertical shaft at the very end of the level. It leads down into a bottomless pit. The shaft serves no apparent purpose and is never seen normally.
Knuckles' ending area and teleporter are all still intact. The teleporter is non-functional however.
IceCap Zone Act 1
Knuckles' starting location can still be found in IceCap Zone even though it goes unused.
Launch Base Zone Act 1
A small level section and spring are in the Launch Base Act 1 layout. Just like Hydrocity Zone, they are completely useless and are never seen because they are overwritten by the Act 2 layout.
There are 3 "end-of-act monitors" hidden in the boss area in the Carnival Night Zone Act 2 contain 10 rings each, curiously there are also monitors in the area of the boss on Angel Island 2 on the way to Knuckles. This is still a total mystery.
Carnival Night Zone Palette
Applying Launch Base Zone Act 2's underwater palette to Carnival Night Zone results in a color scheme identical to that seen in the Nov 3, 1993 prototype and a screenshot of the level found in pre-release material.
Knuckles' theme is just a set of drums that lasts for roughly four seconds, and loops forever. However, at around the 34-second mark is a brief voice sample before the next section of drums. This in and of itself isn't particularly interesting, but it should also be noted that whenever the song plays in-game it's always in scripted events; the song only ever plays for a maximum of 10 seconds or so. The only way to listen to this small sample is to use the sound test, jump just before the bridge collapses in the transition from Angel Island to Hydrocity and land on the piece of land that you fought the boss on and listen to it there, or wait after Knuckles bombs the building near the end of Launch Base Act 1.
While not technically unused, the circumstances to get this would be nearly impossible. Beating a level with a time of 9:59 (1 second from getting a time over) will award the player 100000 points; this also is intentional according to the code.
It would return years later in Sonic Mania.
Changes in Sonic 3 & Knuckles
When locked-on to Sonic & Knuckles, a number of changes were made, either to fix bugs or weird design choices.
Knuckles Art Changes
|Sonic the Hedgehog 3||Sonic & Knuckles|
The Sonic and Knuckles version of his running sprite ended up being polished to be two pixels shorter and fix some of the leftover torso drawing from Sonic's sprite (though they didn't do a good job, as some tan pixels are still present and the diagonal versions weren't changed at all)
Bugs in Sonic 3 Alone
- Due to an oversight, Super Sonic decelerates very fast when rolling.
- In Sonic 3 alone, Super Sonic can bubble bounce, which isn't meant to happen.
- If the W Spin Attack/Insta-Shield animation finishes after Sonic lands on the floor, using it on the next jump won't increase his attack radius.
- For some reason, Checkpoints aren't cleared when returning to the level select in Sonic 3 alone.
- The Bonus Stage title-card will read "Doilus Stage" if the player attempts to quit back to the level select.
- The Big Shaker miniboss in Hydrocity incorrectly plays the Act 2 boss theme, and jumping out of water when you're about to drown will play the Sonic & Knuckles miniboss theme; the latter wasn't necassarily fixed as it's still calling the Sonic 3 miniboss theme, however in Sonic 3 & Knuckles both miniboss themes are the same.
- Tails doesn't have a collision with the wall at the beginning of Hydrocity Act 2.
- It's possible to outrun the trigger to lock the camera at the boss in Hydrocity Act 2. Though this isn't recommended as breaking the capsule will softlock the game.
- The Screw Mobile can glitch out Super Sonic.
- If the Tunnel Bot is defeated too early in Marble Garden Act 2, the game will crash due to the camera being too far away, causing Act 2's level layout to overwrite everything in memory.
- Tails can spawn in weird positions at the beginning of Carnival Night Act 2.
- A ceiling corner in Carnival Night Act 2 has a faulty collision. Should Super Sonic jump into the wall-to-ceiling transfer and run along with the ceiling, he will be stuck in the ceiling, unable to escape.
- If the player glitches Super Sonic into Knuckles' path in IceCap act 1, it's possible for the ice obstacles to hurt him.
- In IceCap Act 1, Tails will die on the first slide. It can be "fixed" by touching the first checkpoint then dying on purpose, or by reaching the first Special Stage (something that's mentioned below the infamous "Eggman's Diabolical Traps" section.
- Super Sonic can be hurt by Big Arms.
- It's possible to clip through the loop in Balloon Park.
There are still more differences.
|Sonic the Hedgehog 3||Sonic 3 & Knuckles|
The beginning of Hydrocity Zone Act 2 went through some layout changes that mostly reduced difficulty.
Marble Garden Zone
|Sonic the Hedgehog 3||Sonic 3 & Knuckles|
In Sonic 3 & Knuckles, a lot of extra objects were added to this room in Act 2 to prevent Knuckles from taking Sonic and Tails' path; the most important object is the GTGT collision block to prevent Knuckles from climbing the wall and hitting the Relief's eye.
- In Act 1, the snow pile that falls on Sonic and Tails in the pit where they enter the cave is not solid in the standalone Sonic 3, but it is in S3&K and it requires the player to jump to get out from it and it can be walked on.
|Sonic the Hedgehog 3||Sonic 3 & Knuckles|
Originally, this was a Sonic & Tails or Tails only path. Sonic 3 & Knuckles added a trampoline so that Sonic can go up there without Tails' help.
Launch Base Zone
|Sonic the Hedgehog 3||Sonic 3 & Knuckles|
Knuckles's boss arena was edited in Sonic 3 & Knuckles. The most notable difference is the position of the Twin Hammer/Swing’m Spikez boxes.
|Sonic the Hedgehog 3||Sonic 3 & Knuckles|
This is another notable difficulty change, as this area is very hazardous in Sonic 3. The player would have to avoid breaking the Eggman monitors and enter a room full of spikes to hit the door switch. Sonic 3 & Knuckles moves the switch outside, and turns the room into a bonus room with two Super Ring Monitors. However, hitting the switch will block off the monitors.
|Sonic the Hedgehog 3||Sonic 3 & Knuckles|
A simple monitor subtype change from a harmful Eggman to a helpful Invincibility.
Unlike other Mega Drive/Genesis Sonic games (including Sonic 3 & Knuckles), Sonic 3 "alone" is region-locked and each region got a separate version.
One difference between the Western and the Japanese release, like Sonic 2, is the name used for Tails (e.g. Tails for US/Europe, Miles for Japan). However, the only change made here is changing Tails to Miles on the Act results; his life counter still says Tails. This was fixed in Sonic 3 & Knuckles.