Sonic Megamix, a fan made mix up of Sonic 1 with Shadow and Mighty added. Well in the weeks since I've discovered there are tons of these fan made games out there. Many are old games with the levels completely changed around to make new games, like Sonic Megamix or Legend of Zelda: Outlands, where as some like this are just old games with different playable characters.
This one has taken Princess Sally Acorn from the Archie Sonic the Hedgehog comic and put her in Sonic 1. That's so damn cool, I've always wanted Sega to use her in the games. The game play is way different. She doesn't use a spin attack when she jumps but rather she can use her handheld computer/sidekick/all purpose tool and weapon Nicole to fire an energy burst to attack what's directly in front of her. I think as I watched the game play she can kill robots by jumping on them with her boots but I'm not sure. You can watch a run through of the entire game here.
I haven't gotten my hands on this game because so far I can only find it for download on my computer or a Sega CD. I want to try and find it as a Genesis cartridge. I might end up giving up and just getting it on my laptop but for now I have hope that someone put it on a cartridge.