Hold the L, R, and Select buttons, then cycle (right) through the racers until you come to Olaf.
Olaf is the large Viking from Interplay's game "The Lost Vikings."
Race On Planet Inferno
On the screen just before you begin your race, go to the planet select screen.
Hold the L, R, and Select Buttons, and then press Right to cycle through the planets while holding these buttons until you come to planet Inferno.