Cheat Mode
Navigate to the "Extras" menu, then select "Codes". Enter the following codes to unlock the the following costumes for purchase:
1585 - Scooby-Doo Egyptian costume.
3726 - Shaggy Native American costume.
2839 - Daphne Karate Black Belt costume.
4826 - Fred Knight costume.
6588 - Velma Pirate outfit.