Sonic the Hedgehog Cheats

Sonic the Hedgehog Unlockable: Shadow the Hedgehog
Finish Crisis City with Sonic.

Sonic the Hedgehog Unlockable: Silver the Hedgehog
You must finish Silver the Hedgehog boss battle with Sonic.

Sonic the Hedgehog Unlockable: Audio Room
You must finish Sonic, Shadow, or Silver's story mode.