Successfully complete all levels except for the Eternal levels. Then, press Circle at the Earth screen for a sound test and FMV sequence viewer. Note: Press Triangle in the Japanese version of the game.
Build the ball up over 1m, 30cm, 3mm in the Make A Star 4 level to unlock the Eternal 1 level.
Build the ball up over 25m in the Make A Star 8 level to unlock the Eternal 2 level.
Build the ball up over 800m in the Make The Moon level to unlock the Eternal 3 level.
After completing the Make A Moon level, replay it and create a larger Katamari. Replace your old Moon with this to view a new FMV sequence.
Once all levels have been completed, replay the past levels. Somewhere on some if not all maps you will be able to pick up a cousin to add to your collection. Note: This was found to be true on the Make A Star 4 and Make A Moon levels.
After completing the game and the credits begin, you can control the Katamari in the background to roll up items.
Set the system date to just before midnight on December 31. When midnight passes, a message from the King of All Cosmos will appear.
While on your home world, allow the controller to remain idle. Your character will begin to move on their own.