Sonic the Hedgehog 3
|Sonic the Hedgehog 3|
Also known as: Baramdori Sonic 3 (KR)
This game has unused areas.
This game has a bugs page
Sonic the Hedgehog 3 is the third game in the 16-bit Sonic trilogy and the first game with the 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 Sonic 2 Menu Leftovers
- 4 Eighth Special Stage
- 5 Unused Objects
- 5.1 Red Revolving Spheres
- 5.2 Carnival Night Button
- 5.3 IceCap Breakable Block
- 5.4 Breakable Wall
- 5.5 Competition Mode Spikes
- 5.6 Carnival Night Ring Object
- 5.7 Unknown Platform
- 5.8 Cannon
- 5.9 Spinning Structure
- 5.10 Grabbable Platform
- 5.11 Leftover Lava Damage Object
- 5.12 Up and Down Spring
- 5.13 Big Sonic on the Sega Screen (Sonic 2)
- 5.14 Shield Object
- 5.15 Other Unused Objects
- 6 Unused Surfboard Intro
- 7 Unused Monitors
- 8 Unused Sprites
- 9 Unused Level Chunks
- 10 Unused Audio
- 11 Unused Palettes
- 12 Scrolling Credits
- 13 Layout Differences
- 14 Unused Areas
- 15 Oddities
- 16 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.
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.
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.
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.
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.
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.
A breakable wall in Angel Island Zone Act. 2 can only be added with debug mode and is destroyed with a Spin Dash on the ground. A similar version is used just like a door that is opened with a switch.
Competition Mode Spikes
A set of spikes for Competition Mode. However, spikes do not appear in any of the five courses, but they can be placed with debug mode.
Carnival Night Ring Object
Unknown object that appears to spawn slope collision when placed.
A platform with messy graphics and a shape similar to a top is identified as object ID 12. This doesn't fit anywhere. This object may have been created for Launch Base Zone because its ID is close to the objects at this level.
A kind of cannon where Sonic is locked in the center of the object, If Sonic runs faster, the launcher will throw him very far. It is identified by ID 1A and its graphics are not identified. It may also have been created for Launch Base Zone.
A curious object that can damage Sonic when he jumps on top, and can swing when Sonic hits it from underneath. Its graphics have not been found, and its animation is of something turning. Identified as Object 1C. It may also have been created for Launch Base Zone.
A normal platform, however it is possible to grab any area below it. Apparently it was created for Launch Base Zone, because some of the graphics seem correct there. Its ID is 1D.
Leftover Lava Damage Object
This object was used in Sonic 1 and Sonic 2 to cause damage to Sonic when he touches lava, but this object does not work. It's possible to change the size of the area by modifying their variable. ID 27.
Up and Down Spring
This object was intended for Flying Battery zone and 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 giant 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 graphics seem to have been completely deleted.
See if this still functioning in the final game.
Code for another shield type 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.
Other Unused Objects
Figure out what the rest of these objects are in Sonic 3C 0408.
There are objects that are never used that are located in the object pointer list. Objects 8F-98 delete themselves once loaded which is rather unusual. One of these objects is used in the Mushroom Valley object layout, suggesting that these were once objects that belonged to the Sonic & Knuckles Zones. Objects 6F-7F are represented as rings in Sonic 3 apparently manually removed, but in Sonic 3C (prototype 0408), these IDs are objects from Flying Battery Zone. Object 84 is another unused and removed object. Based on the fact that it's grouped with bosses and badniks (in the pointer list), it is very likely that it was either a badnik or a boss at one point. By the Sonic 3C 0408 prototype, the original Sonic 3 object pointer list was mostly, or completely overwritten with the one used in Sonic 3 & Knuckles
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. The surfing Sonic sprite can still be placed in Angel Island Zone 1 via debug mode.
The sprites used when Sonic ditches the surfboard.
|Static/blank monitor||An item monitor displaying static that harms you when broken, change a monitor to subtype 00 to view the static monitor.|
|S monitor||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.|
Unused competition mode title cards.
|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 for the Game.com version of Sonic Jam.|
|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.|
|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.|
|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 animations 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 existed in the first place).|
|A set of sprites where Eggman has a panicked facial expression. One of these sprites shows him attempting to jump into a boss machine or Egg Mobile.|
|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. There's actually an object that uses these sprites, but it's never called by any routine.
|Dr. Robotnik poses intended for the unused Flying Battery Zone Act 2 boss. However the left-most sprite goes unused during the boss too.|
|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. 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 1. While the teleporter pad ended up being used in Sonic 3 & Knuckles for Knuckles' transition into the stage, the unusually oversized ice boulder was never used.|
|Some odd unused icons for Competition Mode.|
|While these graphics are later used in Sonic & Knuckles, they go unused in this game. They appear in mangled form in Knuckles's 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. They're used in the final game.
|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. 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.|
|Whatever this is (it vaguely looks like a medal, possibly intended for use in Competition Mode), it's not used. It doesn't even have a known palette.|
|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.|
|A strange arrangement of the spike tiles, which would have been used to make them appear twice as long.|
|This sprite is used in the Launch Base Zone Act 2 laser boss battle, but it is obscured and cannot be seen.|
|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 midboss...|
|...the laser barriers on either side of the arena...|
|...and Eggman's control panel all still exist, but aren't used (except in Sonic & Knuckles).|
|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. This can never be seen because the light bulbs never make contact with the water.|
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.
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:
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.|
|$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.|
|$91||Door closed sound from Sandopolis Zone.|
|$92||Ghost sound effect from Sandopolis Zone.|
|$93||The sound that plays when the armor on Dr. Robotnik's golem machine comes back on.|
|$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 $C4.|
|$C6||The sound that the spiked platforms make when they orbit Red Eye.|
|$CA||The sound of the light beam transportation systems in Death Egg Zone.|
|$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||Possibly unused; 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.|
|$D9||The sound the electromagnets in Flying Battery Zone and the black gravity spheres in Death Egg Zone make.|
|$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.|
Unused PalettesSonic 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.
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 is possible this was once part of the palette used for the removed water in Launch Base Act 1. It can be found at offset 08CB14.
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 in the Sonic 3C 0408 prototype.
Slot Machine Bonus Stage:
This palette is quite different from the Sonic & Knuckles prototypes, and can be seen in offset 08CE14.
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.
When locked-on to Sonic & Knuckles, a number of object layouts are changed in some Acts. Some are minor changes, while others are more significant. These are to primarily adjust difficulty or to allow/deny access to certain routes with certain characters.
|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 being the GTGT collision block to prevent Knuckles from climbing the wall and hitting the Relief's eye.
|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.
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
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.
Knuckles' starting location can still be found in IceCap Zone even though it goes unused.
Launch Base Zone
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.
Carnival Night Zone Palette
Applying Launch Base Zone Act 2's underwater palette to Carnival Night Zone results in a color scheme almost identical to that seen in a screenshot of the level found in pre-release material.
Knuckles Art Changes
|Sonic the Hedgehog 3||Sonic & Knuckles|
The Sonic 3 version is one pixel taller and still has some of Sonic's torso leftover from redrawing. Interestingly enough, the Sonic & Knuckles version still uses the Sonic 3 sprites for the rotational frames.
Unused Super Sonic idle animation
Super Sonic has an extra idle frame and extra colors in his palette cycle that end up going unused for some strange reason. The unused version is a bit smoother than what is actually used.
Knuckles faces the wrong direction
For some strange reason, Knuckles starts off facing the wrong direction before he springs the trap on you. It isn't seen in normal gameplay since Knuckles isn't on the screen at this point and is likely just an oversight.
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.
Like Sonic 2, all versions of Sonic 3 have both English and Japanese content (e.g. "Tails" for US/Europe, Miles for Japan). The content used depends on the console's internal region setting. However, the only change made in this version of Sonic 3 is changing Tails to Miles on the Act results; his life counter still says "Tails". This is fixed in Sonic 3 & Knuckles.