Wire-framed Car
Type "WYRED" at the Begin Career name entry screen for a wire-framed car.

New Opponent
Type "PRESSSTART" at the Begin Career name entry screen for a new opponent.

Fat Cars
Type "PHATCARS" at the Begin Career name entry screen for obese cars.

Cheat Mode
During gameplay, press Pause. Highlight Race Statistics, then press and hold R + C or R + L + A to bring up the cheat menu.

Code - Effect
wyred - Wire-frame mode
phatcars - Very fat cars
pressstart - A new opponent

Bonus Racing Cars
Type "GO BRUINS!" at the begin career name entry screen for six new indy racing cars