Hold A and press Up, Down(4), Up at the title screen while "Press Start" is blinking. Use the D-pad on controller two to change the appearance of the clouds and other effects.
Debug mode
Enable the "Sound test mode" code. Set the options to FM40, PCM12, DA11 and press Start. A screen with Tails will appear. Begin game play, and press B to change into an object, A to select another object, or C to place the object on the screen. While debug mode is enabled, the completion time for each level will be "0:00".
Invisible Sonic
Move behind an object and press B.
Level select
Press Up, Down(2), Left, Right, B at the title screen while "Press Start" is blinking. A sound will confirm correct code entry. Note: Only one level may be played if this code is enabled.
Programmer high scores
Press Right(2), Up(2), Down, C at the title screen.
Sonic Team's Best Times
To see the best times of the game designers, at the title screen press Right, Right, Up, Up, Down, and C.
Sound Test mode options
Press Down(3), Left, Right, A at the title screen while "Press Start" is blinking to display the sound test menu. Set one of the following sound combinations and press Start to enable the corresponding cheat function.
Sounds Effect
FM07, PCM07, DA07 Special levels
FM42, PCM03, DA01 View hidden scene
FM46, PCM12, DA25 View hidden scene
FM42, PCM04, DA21 View hidden scene
FM40, PCM12, DA11 View hidden scene
FM44, PCM11, DA09 View hidden scene
Suicide
Pause game play and press A, B, or C.
Time Attack mode options
Complete the game, then restart the game in "Time Attack" mode. The following options will be available if the "Time Attack" game can be completed within the corresponding time limit.
Music test
Complete "Time Attack" mode within 37:27:57. A "D.A. Garden" option will appear to the left of the "RAM Data" option on the main menu. The Planet of Mobius will be displayed. Hold B and use the D-pad to rotate the planet. Hold C and use the D-pad to zoom in and out. Press A to play the game music.
Play bonus levels
Complete "Time Attack" mode within 30:21:05, then press Left at the "Time Attack" screen.
View video sequences
Complete "Time Attack" mode within 25:46:12. A "Visual Mode" option will appear to the left of "D.A. Garden" option on the main menu. Use this option to view the video sequences in the game.