The following cheats need to be entered at the mode select screen:

Atomic Snowballs: X, X, X, White, Y, Start
Boosts: Y, Black, Black, Y, R, Start
Clone Mode: White, L, L, Y, White, Y, Start
Grappling Hooks: Y, Y, L, Y, Y, White, Start
Invisibility: X, Y, X, R, Y, Y, Start
No Catch Up: Y, X, Y, Y, X, Start
No Drones: X, X, Y, Y, White, Black, Start
Random Location: Black, R, X, Y, Black, R, Start
Rooster Tails: Black, R, L, White, X, Start
Snow Bombs: Y, Y, Black, R, Start
Super Wheelies: Y, White, X, R, X, L, Start