All tracks in arcade mode
Press Left, Right, Left, Right, Up, Down, Up, Down, Triangle(2), X 
at the main menu.


Six cars in two-player mode races
Press Left, Right, Left, Right, Up, Down, Up, Down, Square(2), X 
at the main menu.


Wire frame mode
Press Left, Right, Left, Right, Up, Down, Up, Down, Circle(2), X 
at the main menu.


Win race
Press Left, Right, Left, Right, Up, Down, Up, Down, Square, Triangle, Circle 
at the main menu. Then, press L3 during a race to immediately win. 


Purple rain
Press Left, Right, Left, Right, Up, Down, Up, Down, Up, Down, Circle(3) 
at the main menu.


Cow
Press Left, Right, Left, Right, Up, Down, Up, Down, Up, Down, Up, Down, Circle(3)
at the main menu.