Sonic & Knuckles/Hidden content

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Level select

While in Mushroom Hill Zone, jump on to one of the pulley systems, then press . A Ring sound will confirm correct entry. Press , then to return to the title screen. Press + to go to the Level Select screen.

Though the Sonic the Hedgehog 3 Zones are listed, they are not available unless Sonic 3 is locked-on; selecting any of them will load Mushroom Hill Zone Act 1. The player's character can be chosen by pressing , though selecting 00 or 02 (normally associated with Tails) will override the player's character to Sonic.

Debug mode

Contrary to popular belief, there IS a debug mode available for this game. Sonic the Hedgehog 3 & Knuckles runs on the codebase of Sonic & Knuckles which has a separate check to enable a debug mode cheat code in place of the level select code in Mushroom Hill when Sonic 3 is locked on. To use debug mode purely in Sonic and Knuckles, the player needs to overwrite the memory of the game while a Sonic 3 cartridge or ROM is locked on. Simply start up Sonic 3 & Knuckles, unlock the level select and debug mode codes for that game and then highlight any level in the Sound Test, hold , press , and release when Sonic appears. Switch to an "S" Monitor, and paste a big amount of monitors until sprites begin to flicker. Then revert back to Sonic, and Spin Dash or jump straight into the monitors. Due to how the game loads its art, the game will break, crash or reset to demo mode. If the game has not crashed yet, press , and then press if necessary. The game may ignore any flags for a Sonic 3 cartridge being detected and it will boot up into Sonic & Knuckles mode, redirecting the player to the Sonic & Knuckles title screen. Choose any character, hold then press to go to the level select screen. Highlight any level, hold , then press .

During gameplay:

• Press to reverse gravity when in normal mode.
• Press + to cycle through all mapping frames of the character when in normal mode.
• Press to toggle normal and debug mode.
  • Press to advance forward through the debug object list.
  • Press + to advance backwards through the debug object list.
  • Press to place the selected object at the current coordinates.
• During pause press to fade to black and restart from the SEGA screen.
• During pause press and hold to enable slow-motion (this proceeds at half-speed for as long as the button is held down).
• During pause press to advance one frame.
• Current coordinates are designated by the top line of hex digits in the HUD.
• Viewport coordinates are designated by the bottom line of hex digits in the HUD.

Eighth Special Stage

If Sound Test is enabled, and any of the "Special Stage" options is selected, Sonic or Knuckles is taken to the first Special Stage. The end of it however, spawns a yellow Super Emerald. 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 Sonic & Knuckles alone. This bug will allow access to a hidden Special Stage and allow for the 8th Emerald to be collected once the other six have, though.

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

Hidden area of Hidden Palace Zone

When using edit mode in Hidden Palace Zone, an area above and to the left of Sonic's fight with Knuckles contains a selection of monitors; six on the left, and three on the right. In Sonic 3 & Knuckles, Tails can fly up to this area.

It has been suggested that these could have been placed here so that clean screenshots could be taken for the Japanese manual. The manual clearly shows Sonic bubble bouncing in Hidden Palace, despite no Water Shields being available through normal playMedia:S&K MD JP manual.pdfMedia:S&K MD JP manual.pdf.

Bow to Knuckles

After Knuckles has let the player across in Sky Sanctuary Zone, if the player stands in a certain spot and ducks with , Knuckles turns around and gives a "get going" gesture.

Unused content

Art

Art	Description
	Vertical hanging sprites for Knuckles in Mushroom Hill Zone Act 2.
	A monochrome death sprite for Knuckles.
	An unused, slightly different version of Hey Ho.
	An unused frame for Eggman for use with the Hang Mobile when attacking, but it doesn't appear due to a programming oversight. Pro Action Replay code 067C04:0829 will re-enable it.
	An unused piece of the Egg Golem boss. Its sprite is loaded and the object has a sub-value to load it.
	A jumping frame for Eggrobo.
	Slot machine image for Super Sonic, intended for the Slot Machine Bonus Stage.
	A flashing S gumball. One could presume it has something to do with Super Sonic.
	Unseen palm tree graphics. Although these tiles are used in both Sonic 3 and Sonic 3 & Knuckles in the introduction to Angel Island Zone, they are hidden behind leaf sprites. This is how it looks with the sprites layer disabled:

Objects

Placeable in edit mode

Art	Description
	An "S" monitor. This transforms Sonic and Knuckles into Hyper Sonic and Hyper Knuckles respectively, both of which are normally reserved for Sonic 3 & Knuckles.
	A lava stepping stone for the second Act of Lava Reef Zone. Similar objects exist in Act 1, but this unique art for Act 2 is never seen.
	A platform for the Glowing Spheres Bonus Stage.
	"F" gumball, placeable in Glowing Spheres Bonus Stage. When collected it makes the same noise as a Bumper Ball, but it doesn't do anything.

Others

Art	Description
	A rotating holograph of the Death Egg. It can be found by hex-editing a savestate of Death Egg Act 2. At address A500 replace 01 with E5 and the most northwestern piece will change to this. Thanks to Gold for finding this.
	A solid block that uses art for the slot in the Slot Machine Bonus Stage.

Audio

Audio	Description
	A "game clear" jingle for Sonic & Knuckles at sound ID 32. Though Sonic 3 used this ID for its own jingle played during the ending, 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.

Tails

Tails is playable in the game through hacking. Unfortunately, most of his sprites are missing. A savestate ^(info) (50 kB) of Tails in Sonic & Knuckles is available. If the PAR code FFFF09:02 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's original one). However, his sprites used at the end of Sky Sanctuary Zone to run around the collapsing pillar are actually stored in the Sonic & Knuckles' ROM and therefore are visible. The same sprites are used also in the same context in Lava Reef Zone.

Misplaced objects

Flying Battery Zone Act 1

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

Death Egg Zone Act 1

There are three Rings placed in the floor under the first black anti-gravity orb. It is possible to collect these Rings by returning to this point with a Lightning Shield.

Cheat device codes

These are cheat codes that can only be used with game enhancer devices. Support for these codes is available in most emulators.

Game Genie

Official Codes, Sonic & Knuckles Alone

Code	Description	Works in S&K	Works in S3K
General codes
AFKT-AAG0	Start with 1 life.	Yes	No
AKKT-AAG0	Start with 2 lives.	Yes	No
AVKT-AAG0	Start with 4 lives.	Yes	No
AZKT-AAG0	Start with 5 lives.	Yes	No
A7KT-AAG0	Start with 7 lives.	Yes	No
BFKT-AAG0	Start with 9 lives.	Yes	No
DFKT-AAG0	Start with 25 lives.	Yes	No
GKKT-AAG0	Start with 50 lives.	Yes	No
NPKT-AAG0	Start with 99 lives.	Yes	No
K2WA-CA4J	Infinite lives.	Yes	Yes

Official Codes, Sonic the Hedgehog 3 Locked-on

Code	Description	Works in S&K	Works in S3K
General codes
AWXT-CA4C	Don't lose rings when hit.	Yes	Yes
HXRT-AA6A	Infinite time.	Yes	Yes
96BA-CAG6 + 98MA-CAF0	Keep elemental shields when hit.	Yes	Yes
AKVT-AA76 + AMNA-EA24	Keep rings between levels.	Yes	Yes
RHJA-E60L	Bonus round always activated after every checkpoint.	Yes	Yes
RGSA-A6YY	Only 1 blue sphere needed to get a chaos emerald.	Yes	Yes
ALNA-AACR	Rings worth 2 in special stage.	Yes	Yes
ARNA-AACR	Rings worth 3 in special stage.	Yes	Yes
AWNA-AACR	Rings worth 4 in special stage.	Yes	Yes
A0NA-AACR	Rings worth 5 in special stage.	Yes	Yes
BLNA-AACR	Rings worth 10 in special stage.	Yes	Yes
NTPT-CA50	Rings aren't used up as Super (or Hyper) Sonic/Knuckles.	Yes	Yes
ACCT-CA2R	Can't drown.	Yes	Yes
Sonic-specific codes
RENT-C6YA	Can always double jump (can't use water shield or become Super Sonic).	Yes	Yes
RENT-C6V6	Can always use Fireball Spin Dash (can't double jump, bounce, or become Super Sonic).	Yes	Yes
AANA-CNA0	Jump a little lower (same height as Knuckles jump).	Yes	Yes
4ANA-CRA0	Jump a little higher.	Yes	Yes
2ANA-CWA0	Jump a lot higher.	Yes	Yes
AANA-C4A0	Jump really high.	Yes	Yes
AANA-DYA0	Jump ridiculously high.	Yes	Yes
A2NT-CAG6	Only 6 chaos emeralds needed to become Super Sonic.	Yes	Yes
AYNT-CAG6	Only 5 chaos emeralds needed to become Super Sonic.	Yes	Yes
ATNT-CAG6	Only 4 chaos emeralds needed to become Super Sonic.	Yes	Yes
ANNT-CAG6	Only 3 chaos emeralds needed to become Super Sonic.	Yes	Yes
AJNT-CAG6	Only 2 chaos emeralds needed to become Super Sonic.	Yes	Yes
AENT-CAG6	Only 1 chaos emerald needed to become Super Sonic.	Yes	Yes
AANT-CAG6	Become Super Sonic without any chaos emeralds.	Yes	Yes
NTNT-CAHL	100 rings needed to become Super Sonic instead of 50.	Yes	Yes
FANT-CAHL	40 rings needed to become Super Sonic.	Yes	Yes
DENT-CAHL	25 rings needed to become Super Sonic.	Yes	Yes
BJNT-CAHL	10 rings needed to become Super Sonic.	Yes	Yes
AENT-CAHL	1 ring needed to become Super Sonic.	Yes	Yes
AANT-CAGY + AAPA-CAB8	Become Hyper Sonic without any emeralds.	Yes	Yes
Knuckles-specific codes
TB5T-CNCR	Jumps as high as Sonic (slightly higher than usual).	Yes	Yes
PV5T-CRCR	High jump.	Yes	Yes
AB5T-CWCR	Super jump.	Yes	Yes
AB5T-C2CR	Mega jump.	Yes	Yes
AB5T-DTCR	Orbital jump.	Yes	Yes
A36A-CACW	Only 6 chaos emeralds needed to become Super Knuckles.	Yes	Yes
AZ6A-CACW	Only 5 chaos emeralds needed to become Super Knuckles.	Yes	Yes
AV6A-CACW	Only 4 chaos emeralds needed to become Super Knuckles.	Yes	Yes
AP6A-CACW	Only 3 chaos emeralds needed to become Super Knuckles.	Yes	Yes
AK6A-CACW	Only 2 chaos emeralds needed to become Super Knuckles.	Yes	Yes
AF6A-CACW	Only 1 chaos emerald needed to become Super Knuckles.	Yes	Yes
AB6A-CACW	Become Super Knuckles without any chaos emeralds.	Yes	Yes
NV6A-CADA	100 rings needed to become Super Knuckles instead of 50.	Yes	Yes
FB6A-CADA	40 rings needed to become Super Knuckles.	Yes	Yes
DF6A-CADA	25 rings needed to become Super Knuckles.	Yes	Yes
BK6A-CADA	10 rings needed to become Super Knuckles.	Yes	Yes
AF6A-CADA	1 ring needed to become Super Knuckles.	Yes	Yes
AB6A-CACL + AB6A-CAHR	Become Hyper Knuckles without any emeralds.	Yes	Yes

Unofficial codes

Code	Description	Works in S&K	Works in S3K
General codes
RFLA-A6W4	Enable Level Select (+ at Title Screen).	Yes	No
RFTT-A6XW	Enable Debug Mode (+ at Title Screen).	Yes	Yes
AVFA-AR74	Can Access 'Sound Test' Menu From Title Screen.	No	Yes
AKEA-CA3W	Tails never gets tired of flying	No	Yes
AA7T-AAM2	Better night time	No	Yes
BCTT-LA3Y + BA8T-NA24	Knuckles can fight Knuckles.	Yes	Yes
ABZT-AA5Y + PKZT-B950	Tails follows Knuckles.	No	Yes
REBA-C6V6	Invincible against dynamic objects (bullets, enemies, for example), except Knuckles.	Yes	Yes
RZBA-E6YA	Invincible against static objects (spikes, for example).	Yes	Yes
ABTA-NA7Y	Invincible against Knuckles.	Yes	Yes
PJAA-CA8C	Destroy enemy upon touching it (except Knuckles).	Yes	Yes
ABTT-NA3G	Damage Knuckles upon touching him.	Yes	Yes
AAPT-CAB8	Don't use up rings to maintain the transformation of any Super/Hyper character.	Yes	Yes
CLRA-BA0Y	Get One Emerald To Get Them All.	Yes	Yes
9WSA-BCET	Only One Blue Sphere Needed To Win Emerald.	Yes	Yes
CXLA-EA7Y	Bonus stage is always slot machine.	Yes	Yes
RHLA-E6ZY + BMLA-EA78	Bonus stage is always magnetic orbs.	Yes	Yes
RHLA-E6ZY + RHLA-E6Z8	Bonus stage is always gumball machine.	No	Yes
REPA-C6YR + REPA-C6YT + REPA-C6YW + REPA-C6YY + RFJT-C61Y + RFJT-C610 + RFJT-C612 + RFJT-C614 + RF6T-C6V0 + RF6T-C6V2 + RF6T-C6V4 + RF6T-C6V6 + RHPA-C6V0 + RHPA-C6V2 + RHPA-C6V4 + RHPA-C6V6 + RHPT-C6VE + RHPT-C6VG + RHPT-C6VJ + RHPT-C6VL + RFPT-T6YC	Disable Super Transformation Music	Yes	Yes
NTBT-CB50	Never Die (except by drowning)	Yes	Yes
Sonic-specific codes
JAGA-CA98	Speed shoes don't run out with time.	Yes	Yes
AANT-CAHL	Become Super/Hyper Sonic with 0 rings.	Yes	Yes
AANT-CAG6	Become Super Sonic without collecting Emeralds first.	Yes	Yes
AANT-CAGY + AAPA-CAB8	Become Hyper Sonic without collecting Emeralds first.	Yes	Yes
Tails-specific codes
JA6T-CA5E	Speed shoes don't run out with time.	No	Yes
ABJT-CACJ	Become Super Tails with 0 rings.	No	Yes
ABJT-CACA	Become Super Tails without collecting emeralds first.	No	Yes
Knuckles-specific codes
HKXA-CA7T	Speed shoes don't run out with time.	Yes	Yes
AB6A-CADA	Become Super/Hyper Knuckles with 0 rings.	Yes	Yes
AB6A-CACW	Become Super Knuckles without collecting Emeralds first.	Yes	Yes
AB6A-CACL + AB6A-CAHR	Become Hyper Knuckles without collecting Emeralds first.	Yes	Yes
AB6A-DAJC	Knuckles can float, push any jump button.	Yes	Yes
AP2A-DAR2	Knuckles Spin dash goes nowhere.	Yes	Yes
APYA-DAGC	Knuckles has a shorter glide.	Yes	Yes
AP2A-DAEE	Knuckles flies upwards.	Yes	Yes
1APT-CBHO	Press down for a chaos emerald	Yes	Yes

Action Replay

Unofficial codes

Code	Description	Works in Gens
009760:6048	Red Spheres have no effect in special stages	Yes
0097AE:6672 + 0097C8:4E75	Collision disabled for bumpers in special stage	Yes
FFFE12:0063	Always have 99 lives	Yes
FFFE21:0063	Always have 99 rings	Yes
FFFE25:0000	Infinite time	No
FFB038:00xx	Have character ID of (00=Sonic, 01=Tails, 02=Knuckles) (controls things like wall-breaking and character-specific boss fights).	No
FFFF0B:00xx	Character modifier (00=Sonic & Tails, 01=Sonic, 02=Tails, 03=Knuckles, 04=Blue Knuckles).	No
FFFFE0:0101	Level select and slow motion enabled.	Yes
00380A:???? + FFF65F:0004	Sonic Color modifier (found by tailsisdumb; make sure to replace the ???? with any 4-digit number)	Yes
00381E:0006	Tails is affected by above code (found by tailsisdumb; make sure above code is enabled)	Yes
FFFFDA:0001	Debug mode always enabled (without holding A during level load)	No
FFE439:0001	Only one blue sphere required to get the emerald (turn off as soon as special stage HUD appears or else special stage results screen won't register emerald)	No
FFFFB0:0007	Have 7 Chaos Emeralds.	No
FFFFB1:0007	Have 7 Chaos Emeralds. Use with the code above.	No
FFFFB0:0707	Have 7 Chaos and Super Emeralds.	Yes
FFFFB1:0707	Have 7 Chaos and Super Emeralds. Use with the code above.	Yes
FFFFB2:0?0? + FFFFB4:0?0? + FFFFB6:0?0? + FFFFB8:0?0?	Emeralds in SRAM modifier. Replace ? with 0 = No Emeralds, 1 = All Chaos Emeralds, 2 = Hidden Palace Emeralds, 3 = Hyper Emeralds. Verified to work in Sonic 3 & Knuckles only.	Yes
006B68:0A94	Play as red Sonic (choosing to play as Knuckles produces Sonic with Knuckles' palette) ~courtesy of ShanMan	Yes
FFB15D:FFFF	Blue Knuckles in first save slot. Save slot should be empty. The Blue Knuckles has Sonic's palette, Knuckles' abilities(floating, etc.), Sonic's Sprite in Special Stage, Labeled as Sonic in Lives. The code is pretty unstable, crashes sometimes.	Yes
FFFF09:0003	Same as above.	Yes
FFFF09:00xx	Play as any character regardless of which character is chosen. (00=Sonic & Tails, 01=Sonic, 02=Tails, 03=Knuckles).	No
0119DC:00xx	Transform into Super Sonic with xx emeralds.	No
FFFE10:XXYY	Stage/Act Modifier. X=Level; Y=Act. Set Y to 00 for Act 1, and to 01 for Act 2. ID Name Works in S&K Works in S3K 00 Angel Island No Yes 01 Hydrocity No Yes 02 Marble Garden No Yes 03 Carnival Night No Yes 04 Flying Battery Yes Yes 05 Icecap No Yes 06 Launch Base No Yes 07 Mushroom Hill Yes Yes 08 Sandopolis Yes Yes 09 Lava Reef Yes Yes 0A Sky Sanctuary (Act 1 = Sonic / Act 2 = Knuckles) Yes Yes 0B Death Egg Yes Yes 0C Doomsday Yes Yes 0D Sonic/Tails End Sequence (must be set to Act 2) Yes Yes 13 Gumball Machine - Sonic 3 Bonus Stage No Yes 14 Glowing Spheres - S&K Bonus Stage Yes Yes 15 Slot Machine - S&K Bonus Stage Yes Yes 16 Act 1 = Lava Reef Act 2 boss / Act 2 = Hidden Palace Yes Yes 17 Act 1 = 2nd Death Egg Act 2 Boss / Act 2 = Master Emerald Shrine Yes Yes Garbled in 1P, normal in 2P 0E Azure Lake No Yes 0F Balloon Park No Yes 10 Desert Palace No Yes 11 Chrome Gadget No Yes 12 Endless Mine No Yes	Yes