Duon

Note: I know the this guy doesn't appear in any sonic game, but I though you should know the bosses from Super Smash Bros. Brawl since Sonic is appearing as a playable character. I don't have very much info on this boss, so I'll put in what I can and put more in later. You can battle this boss as anyone in Boss Mode of the game (You must unlock it first though)
1P's Character: Lucario, Snake, Sheik, Peach, Fox, or Falco (you choose three[four if no 2P])
2P's Character: Lucario, Snake, Sheik, Peach, Fox, or Falco (can be any of the other characters 1P didn't choose)

Crazy Hand

Note: I know the this guy doesn't appear in any sonic game, but I though you should know the bosses from Super Smash Bros. Brawl since Sonic is appearing as a playable character. I don't have very much info on this boss, so I'll put in what I can and put more in later. You can battle this boss as anyone in Boss Mode of the game (You must unlock it first though)
1P's Character: Any (you choose before starting Classic Mode[Hard or higher] or Boss Mode)
2P's Character: Any (you choose before starting Boss Mode)