Klonoa

To unlock Balue's tower, free all the six prisioners in every vision (in other words, every one of them)

Collect all six Phantomilians from every Vision.

Translate the book during the credits to unlock bonus costumes.

Successfully complete the final vision to unlock the "Costumes", "Time Attack", "Movie Viewer", "Character Viewer", and "Reverse Mode" options.

All of these extras are unlockable after the main game is completed.

To unlock Lephise's Jukebox you must collect all 6 Phantomilians from every Vision. After doing so, you wil gain a notice saying you have unlocked Balue's Tower as an extra stage. Complete this, then you are rewarded with Lehpise's Jukebox in which you can listen to any great song from the game.