Darth Maul:
Get the top KO score on every track.

Watto:
Get in the fastest three lap times for every track.

Darth Vader:
Unlock Anakin (Episode 1), Watto, and Darth Maul, then win Tournament mode as one of them.

Unlock Episode One Sebulba:
Beat the game with Sebulba.

Unlcok the all Three Art Galleries:
Beat all 13 races in tournament mode.

GameShark Codes

Unlock Darth Vader and Darth Maul
(M) Master Code Must Be On
0E3C7DF21853E59E
EEAF17C6BCDACE32

Unlock Vader
CE5D3F3ABCA99B84

Unlock Maul
CE5D3F2EBCA99B84