Select the 'Extras' option at the 'Main' menu and then enter the following codes to enable the corresponding effect.

Play as Skidmark
Skidmark, Whiplash, Turbo, Burn

Reverse Mode
White Shadow, Turbo, Smooth Move, White Shadow

Turbo's Original Racing Shell
Burn, Smooth Move, Turbo, Burn.

AAA Shell
Chet, Skidmark, Smooth Move, Skidmark.

Firestone Shell
Turbo, Whiplash, Turbo, White Shadow.

New Shell
Skidmark, Whiplash, Turbo, Skidmark.

New Shell
Smooth Move, Turbo, Burn, Smooth Move.

New Shell
Smooth Move, White Shadow, Smooth Move, Turbo.

New Shell
Turbo, Chet, White Shadow, Turbo.

New Shell
Whiplash, Skidmark, Smooth Move, Whiplash.