Here is the full list of all 12 Castle of Illusion Starring Mickey Mouse achievements worth 400 gamerscore.
Bounced on 7 enemies in a row without touching the ground
Defeated Mizrabel and rescued Minnie.
Broke the illusion of 25 enemies with projectiles.
Completed a stage in Time Attack mode.
Found 50% of all Magic Diamonds.
Completed a Castle Statue.
Broke the illusion of 75 enemies.
Unlocked a Castle Painting.
Collect all the Magic Playing Cards.
Collect all of Donald's Chili Peppers.
Complete all Castle Statues.
Find all the Magic Diamonds.