In the game's final level "Make the Moon", a small island can be found and rolled into the Moon called "Demo Island" with the description: "You can play for free, but they won't fix anything if there's a "Technical Issue"." This island is a replica of the map used in a Katamari Damacy demo disc that was shown off and given to attendees at Tokyo Game Show 2003.
Contributed by MehDeletingLater