Sonic the Hedgehog Cheats

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!

Frame By Frame Motion
It doesn't matter when or where you use the code. While the game is paused, (I used a Virtual Console Controller) you can do three things.

Note: The game must be paused for this to work. I am not sure if the Wii Mote will do the same effects. On the Virtual Console Controller:

Y Button = A Button on Sega
A Button = B Button on Sega
B Button = C Button on Sega

Press and Hold [A]: Play In Slow-Motion
Press [Y]: This will reset the game to the title screen
Press [B]: Can Only Press Each Time. Will move onto the next frame

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.

Level Select and Sound Test
At the Title Screen quickly press Up, Down, Left, Right then hold A while pressing + (you should hear a ringing noise after pressing the Control Pad directions.) This will open the the Level Select screen, where you can select any Act, the Special Stage, and the Sound Test. (Note: Controls listed are for the Wii Remote held sideways, the way it is used to play the game.)