All Working Sonic the Hedgehog Cheats - Wii

Drunk Sonic
During the demo, hold [C]. Sonic will crash into walls and get hit by enemies.

Level Select
At the title screen, press Up, Down, Left, Right. You should hear a noise like a ring being collected. Then, hold A and press Start for a level select!

Config Mode (Japanese Version)
At the title screen, press [Up], [C], [Down], [C], [Down], [C], [Down], [C], [Left], [C], [Right]. You'll hear a ring sound. Start the game when holding A to be in Config mode that the Score and Time are distorted. Press B to enable Config mode, that Sonic morphs into a ring. Press A to switch through different items, Press C to place the sprite, hold A and press C to go backwards on selecting items, move around with the D-Pad, or Press B to morph back to Sonic.

Slow Motion and other commands (Japanese Version)
At the title screen, press [C], [C], [Up], [Down], [Down], [Down], [Left], [Right]. You'll hear a ring sound. Pause the game when playing, and hold [B] to play in Slow Motion, press [C] to skip a frame, or press [A] to go back to the Title Screen.

Secret Game Message
At the title screen, press [C], [C], [C], [C], [C], [C], [Up], [Down], [Left], [Right]. When the demo starts, hold [A], [B], [C], [Down] then press [Start]. Instead of the Sonic Team logo, you will see a list of the game's developers in Japanese. When the title screen appears, a flashing "Press Start Button" will be there under Sonic's head.

Unlock Different ending
Beat game with all chaos emeralds.

Glitch: Walk through walls in Marble Zone
When you ride the green block accross a sea of lave, there are a couple of big blocks in front of you with rings on. If you hold the D-PAD [Down] button, Sonic will crouch. The green block will go underneath the blocks, but sonic will remain on it, and pass through the walls. Note that this ONLY WORKS WHILE CROUCHING.