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Sonic & Knuckles

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Title Screen

Sonic & Knuckles

Developers: Sonic Team, Sega Technical Institute
Publisher: Sega
Platform: Genesis
Released in JP: October 28, 1994
Released in US: October 18, 1994
Released in EU: October 18, 1994
Released in AU: 1994
Released in KR: 1994

AreasIcon.png This game has unused areas.
CharacterIcon.png This game has unused playable characters.
GraphicsIcon.png This game has unused graphics.
MusicIcon.png This game has unused music.
DebugIcon.png This game has debugging material.
SoundtestIcon.png This game has a hidden sound test.
LevelSelectIcon.png This game has a hidden level select.

ProtoIcon.png This game has a prototype article

Sonic & Knuckles is a stand-alone expansion pack from Sonic the Hedgehog 3 that is a good game in its own right, but when combined with Sonic 3 becomes what could arguably be the best Sonic game ever.

To do:
Lava Reef Zone Act 2 doesn't fully utilize its palette cycle, leaving half of the colors unused.


Read about prototype versions of this game that have been released or dumped.
Prototype Info

Level Select

Lava Reef 3 = Boss area, 4 = Hidden Palace

The level select can be accessed by starting the game and grabbing one of the lifts in Mushroom Hill Zone. Once the player has grabbed a lift, press Left, Left, Left, Right, Right, Right, Up, Up, Up. If done correctly, a ring chime will play.

When paused, the following actions can be performed:

  • A - Return to title screen.
  • B - Play at half-speed.
  • C - Advance by one frame.

Press Start to pause, then A to return to the title screen. At the title screen, press A + Start to access the level select. From there, pressing C can choose between Sonic (01) and Knuckles (03) only. Trying to select Sonic & Tails (00) or Tails (02) will just give Sonic alone. The Sonic 3 zones are also listed here, but choosing any of them will redirect to Mushroom Hill. Entries in the sound test which normally have songs only heard in Sonic 3 are now empty and unplayable.

Notes about the levels:

  • Lava Reef Act 3 goes to the boss room. Knuckles can't select this level.
  • Lava Reef Act 4 goes to Hidden Palace Zone. Each character goes to their respective entrance in the level.
  • Sky Sanctuary Act 1 is Sonic's level and Act 2 is Knuckles'. Sonic can't go to Knuckles' level and vice-versa.
  • Knuckles can enter Death Egg, but can't defeat the Act 1 boss (Knuckles is unable to jump high enough to hit the boss in the first phase).
  • If Sonic beats The Doomsday Zone, the bad ending plays if the player doesn't have all the Chaos Emeralds.
  • The Doomsday Act 2 leads to the final boss of Death Egg. If Knuckles defeats the boss, the game will reset to the SEGA screen.
  • Knuckles can't enter either level of The Doomsday.
  • Bonus 1 goes to the Glowing Spheres game. Bonus 2 goes to the Slot Machine game. Finishing each stage will restart it.
  • The only remnants of the Sonic 3 zones are the patches made to various zones. These still rely on the data from Sonic 3.

Debug Mode

Debug mode cannot be unlocked by normal means. It can only be unlocked:

  1. By using the Game Genie code RFTT-A6XW then pressing A + Start on the title screen or when in the level select, or the Pro Action Replay (PAR) code FFFFFA:0001 which enables debug mode without the need of a button combination.
  2. By utilizing a glitch in Sonic 3 & Knuckles whereby placing a long string of "S" monitors in a row using debug mode, followed by spindashing into them, will most often cause the game to crash with a garbled screen (though sometimes it will only revoke player control, and other times the player can still play in the Sonic 3 zones until exiting the stage). Pressing the Start button in the first two states (Start + A if Controls haven't been revoked) will load Sonic & Knuckles with level select and debug mode enabled. Using the Wii Virtual Console's "Lock-on Menu", it is shown that the game still thinks that it's locked on to Sonic 3. Likewise, Sonic Mega Collction will also think the same.

When in debug mode, it's the same old songs and dances as the last three games. Normal mode is similar to normal gameplay but with added debug features, while edit mode is a mode where objects can be placed anywhere in a level.

When in normal mode:

  • Press A to reverse gravity (open ceilings act as death pits).
  • Press B to enter edit mode.
  • Press B + C to play through all the frames of the current characters' animations. (May work in edit mode, needs testing!)

When in edit mode:

  • The coordinates of the current object are shown by the top line of hex digits in the HUD.
  • The coordinates of the current viewport are shown by the bottom line of hex digits in the HUD.
  • Press A to cycle forwards through the object list.
  • Press A + C to cycle backwards through the object list.
  • Press B to return to normal mode.
  • Press C to place the current object shown.

Having debug mode enabled disables the lock that prevents Sonic/Knuckles from going into each other's exclusive levels (see above), though in some cases this causes player sprites to become corrupted.

Entering edit mode during some parts of the game (such as the light tubes in Death Egg, and moving far in Flying Battery from the player's death location) will crash the game.

8th Special Stage

S&K unused special stage in game.png The Yellow Super Emerald of Death

If Sound Test is enabled, and any of the Special Stage options are selected, Sonic/Knuckles will be taken to the first Special Stage. The end of it spawns a Yellow Super Emerald however. This is when the Special Stage is marked as clear, but the normal Chaos Emerald amount doesn't rise. The Super Emerald amount will rise, but it has pretty much no effect due to Super Emeralds being unobtainable in S&K standalone. This bug will allow access to a hidden Special Stage and for the 8th Emerald to be collected once the other six have though.

It's also possible to access this Special Stage by enabling debug mode above, then setting the Sound Test selection to 07 and pressing A + Start while selecting any of the Special Stage options.


It's Tails! ...More or less As with Knuckles being unavailable in Sonic 3 but with a few leftovers, Tails is not available in this game. Unlike Knuckles in Sonic 3 however, he's in an actual playable form! Unfortunately, most of his sprites are missing and are replaced with corrupted graphics.

If the Pro Action Replay code FFFF09:0002 is used in Sonic & Knuckles, Tails will be usable, but just about every sprite of his except the transformation sprite will be missing, basically rendering him invisible (unlike when a savestate is used; a different, glitchy sprite is used in place of Tails' original one). There are four exceptions:

  1. Tails' sprites used at the end of Sky Sanctuary Zone to run around the collapsing pillar are actually stored in the S&K ROM, and therefore are visible. The same sprites are also used in the same context in Lava Reef Zone.
  2. Tails' hanging sprites from Sky Sanctuary are also visible.
  3. Tails hanging onto the mushroom paragliders in Mushroom Hill Zone.
  4. In Tails' bad ending, he can be seen normally when Tails and Sonic fly away from the floating island.

Hidden Palace's Hidden Area

Left Right
Knuckles' secret stash. Oh, THERE'S his extra life.

There's a hidden area in Hidden Palace Zone that is only accessible by debug mode or having Tails in Sonic 3 & Knuckles.

Just before entering the inside of Hidden Palace, fly from the two steps left until a ledge is reached. Walk left and six power-up monitors will appear, mostly shield monitors (Ring, Bubble, Fireball). In some of the S&K prototypes, an "S" monitor is present instead of the Speed Shoes.

Two Ring monitors and a 1-up monitor can also be found, on the ledge to the right instead. (video)

Unused Sprites

Sprite Name Description
Super Sonic slot machine panel Reel image for the slot machine bonus stage. Never used in-game.
F-ball An unused gumball intended for the glowing spheres bonus stage. It can be placed in debug mode, but does nothing.
S-ball Another unused gumball without functionality found in the glowing spheres bonus stage.
Platform An unused platform intended for the glowing spheres bonus stage. It can be placed in debug mode, and stood on.
Death Egg Hologram Projector A machine that displays a hologram of the Death Egg, a reference to Star Wars. It can be found by hex-editing a savestate of Death Egg's Act 2. At address A500 replace 01 with E5, and the most northwestern piece will change to this.
Slot machine pocket This object has no functionality and acts like a solid block. It is found in the Slot Machine Bonus Stage with an object ID of 09. It appears to be based on the slot.
SnKHei Hou.png
Hei Hou pieces A set of unused sprites for the Mushroom Hill mid-boss can be found in the Sub-Boss object data. Some sprites have minor differences from the final version. The body and head are displayed as separate sprites here, unlike the final version of the boss.
SnK FBZ2BossHead.png
FBZ2 boss head A sprite from Flying Battery Zone 2's boss which goes unused due to a programming oversight. It can be restored by using the Pro Action Replay code 067C04:0829. Once restored, it will be seen when Robotnik does his swinging attack.
SnKEgg Golem.gif
Egg Golem piece A kind of "screw" that should complete the body of the Egg Golem, the boss of Sandopolis Zone Act 2, is not present, but its sprite is loaded and the object has a sub-value to load it.
SnK LRZ2SteppingStone.png
LRZ2 Stepping Stone A lava stepping stone for Lava Reef Zone Act 2. Though stepping stones appear in Act 1, they don't appear anywhere in Act 2, thus this Act-specific sprite goes unused. It can be placed in debug mode.
Eggrobo jumping Eggrobo never jumps in the game, so this sprite goes unused.
Knuckles intro cutscene Unused Knuckles cutscene sprite for Mushroom Hill Zone Act 2.
S&K-Knuckles death sprite black & white.png
Black & white Knuckles Knuckles also has a black & white version of his death sprite, which, you guessed it, isn't used.
(Source: Sonic Retro)

Hidden Message in Slot Machine Bonus

Japanese characters are used as placeholders for slots animations. Read from top to bottom and from left to right, they are the first few parts of the Iroha poem.

SK Bonus slot machine tiles.png
SK Bonus slot machine tiles big.png

Unused Music

A short "Game Clear" jingle heard by playing sound 32 in the Sound Test. Though Sonic 3 used this sound ID for its own jingle played after defeating Big Arm, it isn't used in Sonic & Knuckles at all. A longer version of this jingle can be heard at the end of the credits medley, though.

Unused Zones

There are a few acts that go unused.

The True Doomsday Act 2

I didn't ask to be thrown out into the void with ZERO rings!

Contrary to what the level select would lead you to believe, the real Doomsday Act 2 is inaccessible by normal means (unless a glitch is used or using patch code FFFE10:0C01). The level is basically empty except for some chunks off-screen. Super Sonic dies shortly after transformation due to being given 0 rings at the start of the level.

Slot Machine Bonus Stage Act 2

Basically the same as the regular version.

Glowing Spheres Act 2

Back to wall dwelling again?

The only major difference is the different spawn point, which is inside a wall.

ID 0D Act 1

Crashes on entry, presumably before the title card even loads. This zone uses Angel Island graphics (which are non-existent in S&K) as a placeholder, which is one of the reasons the Act crashes. The only thing this act is ever used for is giving Hidden Palace its own title card. In Sonic 3, this zone has its own unique ring layout, possibly suggesting it was something entirely different at one point in development. For reference, ID 0D Act 2 is the ending sequence for Sonic.

Gumball Machine Bonus stage

This bonus stage was in Sonic 3 (alone) and in Sonic 3 & Knuckles. It goes absent in this game and simply crashes on the title card, since its data is also absent.

Unused Areas

Lava Reef Zone Act 1


There are three empty bonus rooms in Lava Reef Act 1. They appear to have been used to hold Special Stage rings at some point in development. Inside, there are tunnels that would have allowed the player to enter and exit them, except that they have been blocked off by invisible solid objects. They appear to be remnants from an early version of the stage, like the one that was restored from the Sonic 3 Nov 3rd, 1993 prototype. The locations are as follows:

  1. To the right of the first Spin Dash elevator at coordinates 09C005C0.
  2. To the right of the Spin Dash elevator encountered after the driller badnik, at coordinates 13C00740.
  3. Beneath the crushers on the top path shortly after Sonic's path splits into two, at coordinates 21400540.

Death Egg Zone Act 1

S&K DeathEggUnusedRoom.png

At the top of the first wide conveyor belt elevator sequence in the Act is a hidden room containing two ring monitors and an invincibility monitor. However, the corridor leading to the room is completely blocked off by spikes, making the room impossible to get into without debug mode.

Misplaced Objects

Flying Battery Zone Act 1

Final Sonic 3 Nov 3, 1993 and Final
Combining the Flying Battery layout of Sonic 3 Nov 3,1993 with the objects in final release and then we get a unused thumbnail image in Sonic 3!!!

There are two yellow springs buried in the ground near the first giant purple tube.

Act 1 Act 2
Near the end of Act 1 there are 2 misplaced spikes buried in the ground. Compared to the old prototypes, the level design has not changed. But then how did they get there?
In Act 2 we have the answer; For some mysterious reason the developers misplaced these objects and a copy mysteriously ended up there. Something similar was also seen in Casino Night Zone Act 2 in Sonic 2, where the misplaced rings would fit into Act 1.

Mysterious spikes are hidden in the floor of Flying Battery Zone 1.

Death Egg Zone Act 1

SnK DEZ1MisplacedRings.png

There are three rings placed in the floor under the first black antigravity ball. It's possible to collect these rings by getting a Lightning Shield, and backtracking here.

Sonic 3 Level Select Code

The Sonic 3 level select code is still present in the ROM and can be reactivated via hacking. Interestingly, it was updated to work on the Sonic & Knuckles title, and to be inputted at all times in the Sonic 3 title (unlike Sonic 3 Alone, in which it can only be inputted after the Sega logo but before the title screen appears, which is made harder via the ridiculous number of lag frames).