Lava Mode:
3009DAF0 0001

Gibberish Mode:
3009DAF1 0001

Bonus Track (Note 1):
3009DAF2 0001

Buggy Mode:
3009DAEE 0001

Bike Mode:
3009DAF0 0100

English Mode (Note 2):
3009DAF3 0001

French Mode (Note 2):
3009DAF4 0001

German Mode (Note 2):
3009DAF5 0001

Spanish Mode (Note 2):
3009DAF6 0001

Italian Mode (Note 2):
3009DAF7 0001

Roving Camera (Note 3):
3009DAF8 0001

Arcade Mode Freeze Timer:
800CEB2C 1350

Note 1: To enable this code, it may be necessary to start a race/practice on another track & then abandon it.
Note 2: Only enable one language option at a time!
Note 3: This code is one of the special options, but currently we have no idea what it actually does.