Win all gold medals in the men's and women's events in trial mode. Press L1 or R1 at the character selection screen to access the costume. Note: Using this costume will disqualify you from winning medals or setting records.
Game Shark Codes
Master Code (Must Be On) 0E3C7DF2 1853E59EEE8A6206 BCBBF8CA
Unlock All Characters DE7D424A BBA89A82
Have 99 All Trial Medals BE7D6866 BCBD9BE9935B935B BCA99B83BE7D6862 BCBD9BE9935B935B BCA99B83
Note: Do not save the game when these codes are active.