Unlock Nuclear Bus:
At the Options screen press and hold R & L then enter B, B, Y, A to unlock the Nuclear Bus
Unlock Brick Car:
At the Options screen press and hold L & R then enter B, B, Y, X to unlock the Brick Car
Unlock Soapbox Car:
At the Options screen press and hold R & L then enter B, B, Y, X to unlock the Soapbox Car
See Collision Lines:
At the Options screen press and hold R & L then enter B, B, A, A to see the Collision Lines