Unlock ALL Difficulties, Tracks and Vehicles: Press 'Start' at the 'Title' screen to access 'Mode Select' and then enter L-Shoulder, Z, R Shoulder, Up-C, Down-C, Left-C, Right-C, Start. If you have entered the code correctly you will hear a sound as confirmation.
Unlock Joker Cup: On Expert difficulty setting clear the Jack, King and Queen Cups.
Unlock X Cup: Clear the Joker Cup on Expert difficulty setting.
Unlock Master Difficulty: Win the Jack, Queen, King and Joker Cups on ALL 3 difficulty settings.