At the Options menu, enter JIH345 as your password. To disable, you must reset your PS2.
Ride a Slipknot 'Cycle:
At the Options menu, enter 86657457 as your password.
At the Options menu, enter 23F7IC5 as your password.
Speed Demon mode:
Beat the MX Career mode.
Beat the Freestyle mode.
Ride as Officer Dick:
Beat all the Freestyle competitions.
Thanks to Revolution readers Jimmy tricky, fred86, chills, Donny and PeePerbottle!