Unlock All Tracks in Arcade Mode:
At the main menu press Left, Right, Left, Right, Up, Down, Up, Down, Triangle, Triangle, X
Unlock Cow:
At the main menu press Left, Right, Left, Right, Up, Down, Up, Down, Up, Down, Up, Down, Circle, Circle, Circle
Purple Rain:
At the main menu press Left, Right, Left, Right, Up, Down, Up, Down, Up, Down, Circle, Circle, Circle
Six Cars in 2-Player Mode Races:
At the main menu press Left, Right, Left, Right, Up, Down, Up, Down, Square, Square, X
Wireframe Mode:
At the main menu press Left, Right, Left, Right, Up, Down, Up, Down, Circle, Circle, X
Win Race:
At the main menu press Left, Right, Left, Right, Up, Down, Up, Down, Square, Triangle, Circle. Press L3 during a race to win instantly.