Me And My Katamari Codes -

Katamari Damacy mini-game
Successfully complete the game. After the King speaks during the ending sequence, a short level based on the original Katamari Damacy in classic 8-bit style will begin. You can control the mini-game during the credits by using the D-pad to move and Circle to jump.

Katamari Damacy mini-game: Evening level
Successfully complete the Katamari Damacy mini-game.

Katamari Damacy mini-game: Night level
Reach the Castle in the Evening level of the Katamari Damacy mini-game.

Katamari Damacy mini-game: Dashing
Hold Triangle to hear a little sound and the Katamari should move slightly faster.

Sound Test tracks
Complete the indicated task to unlock the corresponding song in the "Sound Test" option on the "Vacation Memorial" screen.

Blue Orb song: Complete the game and the credits. 
Song For King of Kings: Complete the game and the credits. 

Eternal mode
Get over 80 points as your second score at the end of any normal mode stage to unlock that stage's Eternal version, which removes the time limit.

Alternate name board
Get a 100% object collection by finding each of the 2,434 objects. The island's name board will appear on a strobe light name board instead of wood.