Cheetah car
Enter "NRNNRR" as a password.

Cobra car
Enter "TRTTLL" as a password.

Panther car
Enter "4MSTTR" as a password. Alternatively, enter "YMSTTR" as a password.

Scorpion car
Enter "SDSSRT" as a password.

Unlock Crystal Cup in Grand Prix mode
Enter "LGSSSX" as a password.

Unlock Diamond Cup in Grand Prix mode
Enter "CRKKYY" as a password.

Unlock Zenith Cup in Grand Prix mode
Enter "DZPKKK" as a password.

Master mode and all bonus cars
Enter "PXPRTS" as a password.

All cars and cups
Enter "GGWWOO" as a password.

Enable all codes
Enter "WLLVDD" as a password. Alternately, press Left, Up, Right, Down, Z, R, Down, Left, Up, Right at the player selection screen.