Free Play Mode:
In Free Play mode, you can replay any Main Game stage without having to worry about losing data. You can unlock this by beat the main game.

Secret Kyoto Stage:
In the final stage, Karasuma Keep, knock the Odama through the main gates of the keep to be transported to a secret stage which looks like modern-day Kyoto! It even has the Nintendo of Japan HQ. A Heavenly Odama will crash down for you to knock around and employ Nintendo employees with, for use in the final battle. If you want to leave to get back to the battle, let the Odama roll into the gutter.