Team metal sonic:
Unlock this by getting all 141 emblems then play VS mode 50 times using metal characters (hold A+Y together while choosing level) and team metal sonic will be yours

Metal Sheen
Hold A and Y after selecting a 2-player level to have a "metallic" skin covering over your team.

Super Hard Difficulty
Beat the game with 141 Emblems and all A ratings.

Last Story
Collect all 7 Chaos Emeralds and finish all stories

Two player Team Battle mode:
Collect 20 emblems in single player story or challenge mode.

Two player Special Stage mode:
Collect 40 emblems in single player story or challenge mode.

Two player Ring Race mode:
Collect 60 emblems in single player story or challenge mode.

Two player Bobsled Race mode:
Collect 80 emblems in single player story or challenge mode.

Two player Quick Race mode:
Collect 100 emblems in single player story or challenge mode.

Two player Expert Race mode:
Collect 120 emblems in single player story or challenge mode.

Metallic characters in single player mode:
Collect 141 emblems in single player story or challenge mode.

Follow Me song:
Successfully complete story mode as Team Rose.

Team Chaotix song:
Successfully complete story mode as Team Chaotix.

This Machine song:
Successfully complete story mode as Team Dark.

We Can song:
Successfully complete story mode as Team Sonic.

Team Chaotix FMV sequence:
Successfully complete story mode as Team Chaotix to unlock their FMV sequence in the CG Theater.

Team Dark FMV sequence:
Successfully complete story mode as Team Dark to unlock their FMV sequence in the CG Theater.

Team Rose FMV sequence:
Successfully complete story mode as Team Rose to unlock their FMV sequence in the CG Theater.

Team Sonic FMV sequence:
Successfully complete story mode as Team Sonic to unlock their FMV sequence in the CG Theater.

Super Hard difficulty setting:
Successfully complete the game with all "A" ranks and 141 emblems.

Hint: Defeat Metalmadness:
As Team Rose, break one of the boxes to get Team Blast. Get close to him in Power or Fly formation on the edge. Use it, then change to Fly formation attack until you are not invincible. Do the same thing again with the other box, then keep attacking in Fly formation close to him. If you get hit, get back on the stage and avoid the rest of his attacks. Get the rings and try again. Eventually he will lose his 100 HP on that side. Then as Team Chaotix, the color...