Sonic & Knuckles Collection/Hidden content

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Level select

SK level select.png

While in Angel Island Zone in either Sonic the Hedgehog 3 or Sonic 3 & Knuckles, jump on to one of the swinging vines, then press  🡨   🡨   🡨   🡪   🡪   🡪   🡩   🡩   🡩 , and a Ring sound will confirm correct entry. Next, press  Alt  +  R  to soft-reset the game and return to the title screen. After being taken back to the title screen press  🡫  twice and select the Sound Test option.

In Sonic 3 & Knuckles, any Zone can be selected. When playing Sonic 3, Zones from Sonic & Knuckles can't be selected (Flying Battery, Mushroom Valley, Sandopolis and Bonus).

In Sonic & Knuckles, the same code can be performed on the pulley lifts in Mushroom Hill Zone. However, unlike the Mega Drive Version, there is no way to access this screen in Sonic & Knuckles alone since there isn't both an A & Start button for the player to use, unless Debug Mode is enabled in the S3K.ini file (details below). Note that starting a Sonic & Knuckles game with Debug Mode enabled initially loads the Sonic 3 & Knuckles level select (allowing Sonic 3 zones to be selected), so in order to access the Sonic & Knuckles version, press  Alt + R  to soft reset, then input the code in the usual way. This programming oversight also allows Sonic 3 & Knuckles exclusive codes to be used in Sonic & Knuckles (details below)

Play in any level as any character / enable special stage selection


In Sonic 3 & Knuckles, start the game with the any character. Enter the Zone select code and then soft-reset the game. At the title screen press  🡩  to be taken to the Zone Select menu. Normally, specific levels can't be chosen with specific characters (I.E. Knuckles in The Doomsday Zone). Go to Mushroom Hill Zone. Grab onto a pulley and re-enter the Zone Select code. Now go back to the Zone Select menu. Now, any Zone will be playable using the character that was chosen.

This code also enables a special stage selection feature in the stage select menu. Set the sound test value to the number of the special stage you wish to play (00 = special stage 1, 01 = special stage 2, etc) then highlight 'Special Stage 2', hold A (default Numpad  1 ) and press Start (default  Enter ). Note that this feature can only be used if debug mode is enabled as the additional Mega Drive buttons are required.

Extra special stages


There are two hidden special stages in the game, one in Sonic 3 and one in Sonic 3 & Knuckles / Sonic & Knuckles, both accessed in the same way.

If playing Sonic 3 & Knuckles, enable the special stage selection code above (Sonic 3 does not require this step), set the sound test value to '07' then highlight 'Special Stage 2', hold A (default Numpad  1 ) and press Start (default  Enter ). Note that this feature can only be used if Debug Mode is enabled as the additional Mega Drive buttons are required. Also note that the Sonic 3 hidden special stage uses the Sonic 3 & Knuckles palette rather than the Sonic 3 palette.

An alternative way to access the Sonic 3 & Knuckles stage is to simply select 'Special Stage 2' without using the special stage select code at all. The secret special stage is the default in this game (unlike Sonic 3 where the code must be used.)

The special stage can only be accessed in Sonic & Knuckles by using 'Sonic 3 & Knuckles codes in Sonic & Knuckles' exploit (details below) to enable the special stage selection code.

Start with all Chaos Emeralds collected (Sonic 3 Only)


Access the stage select, go to the sound test and play sounds 02, 04, 05 and 06. A Chaos Emerald sound will confirm correct entry. Note that this feature can only be used if debug mode is enabled as the additional Mega Drive buttons are required to play the sound effects.

Secret INI file settings

By creating a file in the folder C:\Windows (where C:\ is the main partition for Windows) named "S3K.ini", additional cheats can be enabled by adding options to the file, similar to the special debugger option in the Sonic CD INI file. Type the following into the file:


Nine options can be configured here:

  • DebugMode: Enables debug mode. When enabled, numeric keypad keys  1 ,  2 , and  3  act like Mega Drive buttons A, B, and C, respectively, so the player must make sure  NumLock  is turned on (The other keys maintain their configuration as set in the Options menu). When any of the games are loaded, they will begin from the level select screen instead of the Sega logo. From there, edit mode will be turned on automatically when entering any level. During gameplay:
    • Press Numpad  1  to reverse gravity.
    • Press Numpad  2  to toggle object placement mode.
    • In object placement mode, press Numpad  1  to move forward one object.
    • In object placement mode, hold Numpad  1  and press Numpad  3  to move backward one object.
    • In object placement mode, press Numpad  3  to place the selected object.
    • You start Doomsday Zone with 500 rings instead of the usual 50.
  • EnableFrameDrop: Enables frame dropping. Sonic & Knuckles Collection is unplayable in windowed mode on computers with a CPU faster than 350 MHz because it lacks a speed-limiting feature in this mode. However, the timings used by full screen mode are based on the monitor's refresh rate, so the game can be played at the correct speed at a 60Hz refresh rate on any modern system. Enable this to play in windowed mode at a perfectly playable speed.
  • MukaiDropFrame: This option is enabled by default, and allows for a higher framerate on slower machines (by 1997 standards); however, on modern systems, it makes the game run too fast. Set to "0" to disable it and restore a proper framerate in windowed mode on modern systems.
  • ShowFrameCount: Shows an FPS counter onscreen. This will obstruct the game screen, but if debug mode is turned on then the game screen will be shifted down the window to allow the FPS counter to display without covering anything up.
  • EnableFrameCapture: If set to "1", the game will map  F9  to a screenshot function. Press  F9  at any time while playing to take a screenshot in Windows BMP format. Screenshots are saved as "Cap(5-digit_number).bmp" in the game's directory.
  • UseModeX: Use VGA Mode X for 320x240 in fullscreen. Probably not useful on systems running Windows NT-based operating systems (e.g. Windows XP and later).
  • NoSoundEffect: If set to "1", disables sound effects.
  • CDCheckEnable: If set to "1", requires the Sonic & Knuckles Collection CD-ROM to be present. Set to "0" to disable the CD check.
  • SonicGameMode: Default game mode to use when starting SONIC3K.exe directly. Set to "0" for Sonic 3 & Knuckles (default), "1" for Sonic & Knuckles, or "2" for Sonic 3.
  • BGMMode: Specifies which music setting will be used. "0" disables music, "1" uses FM synthesizer music, and "2" uses general MIDI music.
  • GameMode: Specifies which mode the game will start up in. "0" is the full version, "1" is demo mode, and "2" is trial mode.
    • In demo mode, all controls are disabled so only the title screen and rolling demos can be viewed. Used for demonstration purposes.
    • In trial mode, only the single-player mode of Sonic 3 & Knuckles can be played, and only Angel Island Zone is playable without saving. After clearing Act 2, the game ends with a dialog message, then returns to the title screen.
  • LangMode: Specifies the game language. "0" is English, "1" is French, "2" is German, and "3" is Spanish.

This makes some codes or functions that were originally impossible, such as the level select in Sonic & Knuckles alone, switching characters in the level select menu, and Night Mode (Sonic 3 only) possible. It also allows use of the level select's Sound Test option during the actual game.

Sonic 3 & Knuckles exclusive codes in Sonic & Knuckles


As mentioned in the level select section above, starting a Sonic & Knuckles game with Debug Mode enabled will load the full Sonic 3 & Knuckles level select. Soft resetting at any time using  Alt + R  will restore Sonic & Knuckles behaviour, but any code you input before then will be remain enabled. Inputting the Sonic 3 & Knuckles level select code will enable the Sonic & Knuckles level select after a soft reset.

If you enable the level select, then subsequently lose all lives to get a game over and return to the level select, you can access Mushroom Hill Zone and enable the any level as any character/special stage select code, which is also retained after a soft reset. This code cannot be enabled in Sonic & Knuckles by normal means.

Knuckles in Sonic 3

S&KCollection PC KnuxInSonic3.PNG

Sonic 3 had leftover code for Knuckles, but attempting to select him in the Mega Drive original would load Sonic instead. With the help of a save file editor, one can edit values for save files in the game. (It is also possible to use other methods of editing by modifying the Sonic3K.bin file, but editors are generally more user-friendly.) Because Knuckles (and Flying Battery Zone) was planned for and still have existing data in Sonic 3, he is a selectable values when editing saves. Unlike the original game, however, the gameplay engine used for Sonic 3 in this specific compilation is actually based upon the Sonic & Knuckles engine, therefore Knuckles can be played as in Sonic 3 without error.

However, because only Sonic/Tails' boss triggers are in place, Angel Island Zone Act 2 and Launch Base Zone Act 1 are impossible to complete as Knuckles. For some reason, Knuckles's boss for Angel Island Zone Act 1 is still present. Launch Base Zone Act 2 can't be completed without gliding over to Sonic's boss area from his boss area and clearing the game with Knuckles will cause it to crash since he never had an ending programmed for Sonic 3 alone.

The 'Special Stage Mode' feature can be exploited to force this behaviour without editing any files. Access 'Special Stage Mode' from the Sonic 3 stage select by selecting 'Special Stage 1'. Press  🡫  to highlight 'code' then press Jump (default  Enter ) to switch character from Sonic to Knuckles. Now soft reset by pressing  Alt + R  then start a new game from the level select menu to play as Knuckles. Starting a new game from the main menu disables this exploit, the level select must be used.

Flying Battery Zone in Sonic 3

S&KCollection PC FlyingBatteryInSonic3.png

Like with Knuckles, Flying Battery Zone is playable in full form and can be accessed using an external save editor to make a Sonic 3 save which is set to start at "Zone 5" – Flying Battery, complete with the unused Sonic 3 Data Select icon.

Flying Battery is sort of an odd stage in Sonic 3. Clearing it and resetting the game will advance the player to the IceCap Zone. Continuing to play it after clearing it will allow the player to play through the remaining Sonic & Knuckles Zones in Sonic 3 mode, starting with Sandopolis Zone. Clearing these Zones will give the player the normal Sonic 3 & Knuckles credits and ending based on how many Chaos Emeralds the player has collected, but when they get back to the Data Select screen, the palettes turn pink and the file that the player was using is redirected to Marble Garden Zone for some reason. Furthermore, once the player clears Flying Battery Zone, it can't be accessed again unless another file is created that can access it.

Another oddity with the S&K Zones in Sonic 3 is that Giant Rings are only usable if the player has less than 7 Chaos Emeralds, a behavior also exhibited by the Sonic 3C prototypes. If the player has all 7, they simply get 50 Rings.

Unused content


Track #44 in the sound test is normally reserved for the mini-boss theme in the original Sonic 3, but in this version it is an entirely different song that isn't used anywhere in any of the games (this version of Sonic 3 uses Sonic & Knuckles' mini-boss theme). Interestingly, the 1993-11-03 prototype of the Mega Drive version also contains this song where the Sonic 3 mini-boss theme would normally go.

See also


Sonic & Knuckles Collection
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