Enter following codes during gameplay. Keep in mind that the below listed codes last for 30 seconds only:

Monster Truck
L1 (2), Left, Right, L3 (4).

Trippy Camera
L1, L2, R1, R2, Left (2), Up (2).

Big Heads
Triangle, Square, X, O (2), X, Square, Triangle.

Low Rider
Up (2), Down (2), X, O, Triangle, Square.

Trike Cam
Up (2), Left (2), R1, R2, L1, L2.

Invisible Car
Up, Right, Down, Left, L3, Left, Right, Left.

Funny Cars
Up, X, Down, Triangle, Left, O, Right, Square.