Depending on which file you choose at the load screen, "Na", "M", or "Co", you will get a different start up sound. It is cats meowing for the first file, cows mooing for the second, and chickens clucking for the third.
Alternate title screen
Successfully complete the game to alternate the title screen.
Bonus movie
Successfully complete the Cousin Collecting level to unlock a second bonus movie.
Comet level
Successfully complete the game, then talk to the astronaut to play the Comet level.
Comet shower
To use the Comet Shower you must unlock all of the comets by completing levels in the game, by a certain amount of time. After unlocking all of the comets go to the planet viewer and use every comet by pushing a certain button. The Comet Shower should begin.
Comet storm/alternate cosmos perspective
Get all the comets, then visit the Cosmos screen. Press the corresponding buttons to "shoot" all the comets (the order does not matter). You will see a comet storm followed by a shift in perspective. This new perspective displays the cosmos as two perpendicular orbits.
Cousin Collecting level
Find all the cousins, then talk to the boy with the yellow shirt to play the Cousin Collecting level.
Memorial option
Successfully complete the game to unlock the "Memorial" option. Select it to access the game's music and movies.
Million Roses level
Successfully complete the Cousin Collecting level, then talk to the rose to play the Million Roses level.
Original Katamari Damacy constellations
Have a saved game file Katamari Damacy on your memory card to unlock an option at the data screen that will allow you to import your constellations from the original game.
Save The Earth level
Successfully complete the game, then talk to the astronaut to play the Save The Earth level.
Staff Credits level
Successfully complete the game, then talk to the girl with the yellow shirt to replay the level that featured the game's credits.