Start Sonic The Hedgehog and Sonic 3D Blast twenty times each.
Comix Zone (Japanese version)
Select manual mode, then press Z(3), Up(3), Down(3), L, R, Z. A sound will confirm correct code entry.
Debug - S3K
Start a 1-player game on AIZ and grab a swing.While swinging, press left left left right right right up up up. You will hear a ring sound if entered correctly. Then pause and press A to return to the title screen. Press down twice to highlight the sound test you unlocked and press start. Select Mushroom Hill and do the same thing on the first thing you can hang on to (like the swing vines in AIZ). Do the same 3 left 3 right 3 up pause and press A. Go to the sound test and simply hold down A while selecting a level. Also while on level select, press C to change character. 00 = Sonic & Tails 01 = Sonic 02 = Tails 03 = Knuckles.
Knuckles In Sonic 2
Unlocked in the process of starting Sonic Spinball and Sonic 2 fifty times.
Start the following games fifty times: Sonic The Hedgehog, Sonic The Hedgehog 2, Sonic The Hedgehog 3, Sonic And Knuckles, Sonic 2 And Knuckles, Sonic 3 And Knuckles, Sonic 3-D Blast, Sonic Spinball; and start Blue Spheres 30 to 40 times.
Code - Effect
XXXXXX - Cancel all codes
MUSEUM - Fight only bosses
ILOVEU - Level select
MIEMIE - See hidden items
SUPER - Super hard mode
DOFEEL - Time attack
MAGURO - Tone deaf sounds
SUPERB - Very hard difficulty
Sonic 1 Debug Mode
First go to the Sonic 1 title screen and press Up, X, Down, X, Left, X, Right, Up, X, Down, X, Left, X, Right, X. Now HOLD B and press Start. Now when the game starts press A to go to debug mode.
Sonic 1 Pick Level & Sound Test
First go to the Sonic 1 title screen and press Up, Down, Left, Right. Now hold B to pick a level & get sound test.
Sonic 2 Debug Mode
First go to the Sonic 2 Sound Test screen and play sounds 01, 09, 09, 02, 01, 01, 02, 04. Now at the sound test screen hold B and pick a level and Start.
Sonic 2 Pick Level
First go to the Sonic 2 Sound Test screen and play sounds 19, 65, 09, 17. Now hold X and press START. Now on the title screen hold B and press START.
Sonic 3 - Debug Mode
Go to the Stage Select screen and hold button B. Then pick a level and start.
Sonic 3 - Get Extra Stage
After doing the Pick Level code/cheat, go to the Sound test screen and play sounds 01, 03, 05, 07. Now highlight Special Stage 2 and hold B and press START.
Sonic 3 - Pick Level
As you hear Sega spoken but BEFORE the main menu appears press: Up, Up, Down, Up, Up, Up. Then at the title screen press Up to get Stage select and Sound Test.
Sonic 3 & Knuckles: Glich Galore
First, use the level select code and go to Doomsday 1 with Knuckles and beat that level and you will see 2 Master Emeraids and more.
Sonic 3 And Knuckles:
Unlocked sometime in the process of starting Sonic 1, Sonic 3, Sonic And Knuckles, and Sonic 3-D Blast fifty times.
Sonic and Knuckles - Level select
Start a game with Sonic and run over to the Madmole near the Super Shoes power-up. Directly to the right of the Madmole is a pulley mechanism that takes you to the next level above by pushing Down on it. Instead of pushing down, push the Left, Left, Left, Right, Right, Right, Up, Up, Up. Now press Start to pause the game and press B. You will be sent back to the main screen. When you can select between Sonic and Knuckles, hold B and press Start for a level select.
Sonic The Hedgehog - Cheat Mode
At the Sonic The Hedgehog title screen, press Up, Down, Left, Right. Hold B for level select and sound test.
Sonic The Hedgehog - Debug mode
At the Sonic The Hedgehog title screen, press Up, X, Down, X, Left, X, Right, Up, X, Down, X, Left, X, Right, X, Now hold B and press Start. Press A to enter debug mode.
Stop Time in Sonic 2
Pause the game and hold A for the rest of the stage to play without time passing. Press X to jump and spin dash while holding A. You will move without time passing, but the enimies will still move. To stop the game just relese A.
The Ooze (Japanese version)
Select options mode, then press Up, L, Down, R, Up, Z, Down, L, Up, R, Down, Z. A sound will confirm correct code entry.