Micro Machines cheats and cheat codes for Gamecube

Unlock Hovercar:
Play in challenge mode and win the Platinum Cup.

Unlock new vehicle:
Play in championship mode and win the Platinum Cup

Find the three hidden stars on the indicated level in single palyer mode
to unlock new features:

Big Heads: Find the 3 secret stars in This Ol' House GP.
Bird's Eye: Find the 3 secret stars in Perilous Places GP.
Color Tint: Find the 3 secret stars in Hoedown GP.
Concept Art: Find the 3 secret stars in Jungle Jamboree GP.
Earn The Team: Find the 3 secret stars in Graveyard GP.
Micro Marble: Find the 3 secret stars in 911: Emergency GP.
Micro Soccer: Find the 3 secret stars located in Beachside GP.
Mirror Tracks: Find the 3 secret stars in Toy Town Sci Fi GP.