Enter the following as your name when you start a new season.
Code - Effect
AIRFILLED - Moon Gravity Mode
ELGNUJ - Jungle Track
INCORPOREAL - Pass through other cars
LEADSHOT - Super Gravity Mode
MOOBMOOB - All cars
MOONEY - Normal Gravity
PREALL - All Tracks and Cars
PREPRO - All pro level cars and tracks
PREVET - All veteran level cars and tracks
SISAO - Unlock Oasis Track
bsirch - Hillside
cire - Dry Humps
foster - Little Woods
kcin - Rock Creek
mit - Dusty Road
nivek - Frozen Trails