At the Options screen, press F1. Now enter the 
following codes: 

GLASSX - Crystal cup
ROCKYY - Diamond cup
ZDPEAK - Zenith cup
DESERT - Scorpion car
RATTEL - Cobra car
XPERTS - All Cups and Mirror Mode
RUNNER - Cheetah car
ALLVID - All Cars and Cups
MYSTER - Panther car