Sega Dreamcast:

Sonic Adventure 2:
Boss Attack Mode:
To unlock Boss Attack mode, complete either Hero or Dark side story modes. You'll be able to fight each boss from either Hero or Dark side.

Unlock Last Stage:
In order to play the actual last stage of Sonic Adventure 2, finish both Hero and Dark side story games. Once done, go into story mode and a "Last Stage?" menu selection should appear between Hero and Dark selections.

Unlock Dark Garden:
To unlock the Chao Dark Garden, you must raise a Dark Chao with one of the three Dark characters. Continually feed and train your Dark Chao and it should evolve (creates a tear-shaped "cocoon"). Once it evolves, descending stairs should appear at the main Chao lobby leading to the Dark Garden.

Unlock Hero Garden:
To unlock the Chao Hero Garden, you must raise a Hero Chao with one of the three Hero characters. Continually feed and train your Hero Chao and it should evolve (creates a tear-shaped "cocoon"). Once it evolves, ascending stairs should appear at the main Chao lobby leading to the Hero Garden.

Unlock Kart Racing Game:
In order to unlock the Kart game, in the Hero Side story, complete Tails driving quest and in Dark Side story, successfully finish Rouge chase mission.

Sonic Shuffle:
Bonus Characters for Versus Mode:
You can unlock new characters for the Versus Mode by purchasing pictures in Sonic's Room. For example, if you buy all pictures of Tails, you unlock Big the Cat. The following characters are available: Big the Cat - Buy all pictures of Tails Chao - Buy all pictures of Knuckles E-102 Gamma - Buy all pictures of Amy Super Sonic - Buy all pictures of Sonic

Disc Artwork:
To discover some hidden artwork on the disc, put it into your PC CD-ROM. The images will be labeld C20.bmp and so on.


Sega Genesis:

Sonic 1:
Level Select:
At the title screen,press UP,DOWN,LEFT,RIGHT,then hold DOWN A and press start.A ringing sound confirms the trick and a Stage Select menu appears.

Sonic 2:
Level Select:
Go to the Sound Test on the Options screen and then use Button B to play the following sounds in this order: 19,65,9,17. A ringing sound confirms the trick.Press START and when the Title Screen reappears,hold down A and press START to make a Stage Select screen appear.

Instant Super-Sonic:
To begin the game with all the Chaos Emeralds collected,enter the above Level Select code.At the Level Select screen,highlight the new Sound Test and play the following sounds in this order: 4,1,2,6. Begin your game on any level,and once you've collected 50 rings,you'll become SUPER-SONIC!

Debug Mode:
To enter Debug Mode, play these sounds from the level select screen: 1, 9, 9, 2, 1, 1, 2, 4. Press Start and hold A.

To start debugging, press B, then you can select any sprite in that level and put it on the screen. To select a different sprite, press A, and to place it on the screen, press C. Note that sprite selection is different from Zone to Zone. Also, instead of displaying the time elapsed, it displays the number of sprites currently on the screen.


Sonic 3:
Debug Mode:
Before Sonic appears fully on the Title Screen,press UP,UP,DOWN,DOWN,UP,UP,UP,UP.Note that this is extremely tough to do.If you entered the code correctly,you'll hear a ringing noise and you can select the Sound Test option at the Title Screen.The Sound Test lets you select any level(except Sandpolis Zone and Mushroom Valley).Highlight the level,hold down A,and press START.Press A to change the sprites,B to become the sprite,and C to duplicate the sprite.

Sonic Spinball:
Level Select:
Go to the Options screen and press A,DOWN,B,DOWN,C,DOWN,A,B,UP,A,C,UP,B,
C,UP.You'll hear a special tune if you entered the code correctly.Go back to the Title Screen and hold down,Aand press START to begin on level 2,hold down B,and press START to begin on level 3,hold down C,and press START to begin on level 4.

Sonic 3D Blast:
Level Select:
At the Title Screen,press B,A,RIGHT,A,C,UP,DOWN,A.That spells,"BARACUDA".Press START and then press it again where it says the word,"START".

Sega Saturn:

Sonic R:
Secret Characters:
Metal-Sonic:
Go to Resort Island.Get all 5 Sonic Coins and get in 3rd place or better.Then Metal-Sonic will challenge you to a race.If you win,you'll have access to Metal-Sonic.

Metal-Tails:
Go to Radical City.Get all 5 Sonic Coins and get in 3rd place or better.Then Metal-Tails will challenge you to a race.If you win,you'll have access to Metal-Tails.

EggRobo:
Go to Regal Ruin.Get all 5 Sonic Coins and get in 3rd place or better.Then EggRobo will challenge you to a race.If you win,you'll have access to EggRobo.

Metal-Knuckles:
Go to Reactive Factory.Get all 5 Sonic Coins and get in 3rd place or better.Then Metal-Knuckles will chalenge you to a race.If you win,you'll have access to Metal-Knuckles.

Dr.Robotnik:
Beat all the other levels and get in 1st place.Then you'll have access to the Radiant Emerald level.Beat the level and get in 1st place.You'll have access to Dr.Robotnik when you beat it.

Be The Same Character:
At the character select screen,one of the players choose the character.Then the second player will put the cursor on the charater that the first player picked.Second player should hold button Y and press A and B buttons at the same time.