The following codes must be entered at the main menu:
L1, R2, L1, R2, Square, Select.
Naboo Kaadu Racers
L1, R1, L2, R2.
Space Freighter Arena
L1, R1, Select, Circle.
Unlock Galaxy Circuit
If you qualify into the top three on all of the tracks in the game, the Galaxy Circuit will be opened.
Darth Vader and Mirror Mode
To race as Darth Vader finish the GALAXY challenge with a gold medal, and with Anakin Skywalker, Darth Vader should be available. At the same time a Mirror Mode should open up, because you've completed the Galaxy circuit.