Enter these as your name in the "create driver" screen:
BANZAI : No collisions with other cars
FAT WHEELS : Fat back wheels
FEATHER : When you flip over you can't get back up
FLOT : 1/2 gravity
GEK : 2 lap races
IMMORTAL : Invulnerability
PUSHBUTT : Dual-analog controls
RADBRAD : Better gravity
STONE : 2x gravity
WHEELS : Only the wheels are visible
WINNER : Win the race