To get Robot Outfit, use trial mode to get all gold medals in the men's & Women's events. At the character select screen press L or R for the outfit.
To get Bear Outfit, use championship mode to get all gold medals in the men's & Women's events. At the character select screen press L or R for the outfit.
To get Penguin Outfit, use championship mode to get all gold medals in the Women's events. At the character select screen press L or R for the outfit.