The S Factor: Sonia and Silver (Hack Playthrough) 

Silver's learned how to do that spinny jump, which in the Sonic world, I imagine is like learning to ride a bike. He's still got his old tricks though.
This is a hack with completely new music and levels, and bosses too. It also adds two playable characters, whose names I'm sure you can guess.
Hack is made by Aquaslash & Pals, get it here! info.sonicretro...
Note: Some editing has been employed to erase an hour and a half of failures. I'll bet you can figure out where.