Alternate Game Select Screen Music - To unlock different music for the Game Select screen (the Corkboard), beat The Arena once.

Golden Frame on Corkboard - If you get 100% in your file, the Corkboard will have a golden frame around it

Sound test - After completing Milky Way Wishes, you unlock the sound test. It lets you lisen to all the songs and sounds in the game

Sound Test Complete Milky Way Wishes

Unlock new games - Complete the following tasks to fufill the requirements to unlock these games.

Dyna Blade Beat Spring Breeze
Gourmet Race Beat Spring Breeze
Helper to a Hero Complete The Arena.
Megaton Punch Complete The Arena.
Meta Knightmare Ultra Complete Revenge of the King.
Milky Way Wishes Beat Spring Breeze, Dyna Blade, The Great Cave Offensive,Gourmet Race, and Revenge of MetaKnight
Revenge of MetaKnight Beat Spring Breeze, Dyna Blade, The Great Cave Offensive, and Gourmet Race
Revenge of The King Complete Milky Way Wishes.
Samurai Kirby Clear Meta-Knightmare Ultra.
Sound Test Clear The First six games.
The Arena Complete Milky Way Wishes.
The Great Cave Offensive Beat Spring Breeze
The True Arena Complete The Arena, Helper to Hero, Revenge of the King and Meta Knightmare Ultra

Unlockable Bonus Films - Throughout the course of the game you can unlock little films in the Theater mode where you can watch hidden videos in the game or the past cutscenes. Below is the film name and how to unlock them.

Dyna Blade Play through Dyna Blade
Flying Fortress Kabula Play through Revenge of the King
Friends and Sun Complete Revenge of Meta Knight
Gourmet Race Play through Gourmet Race
Grand Opening Simply watch the opening of the game
Great Cave Offensive Play through the Great Cave Offensive
Great Escape-Hero Up High Beat the Great Cave Offensive
Halberd Scenes 4-6 Play through Revenge of Meta Knight
Halberd Scenes 1-3 Play through Revenge of Meta Knight
Halberd Scenes 7-9 Play through Revenge of Meta Knight
Kirby's Triumphant Return Complete Milky Way Wishes
Live Healthy Defeat Dyna Blade
Marx's Mad Plan Play through Milky Way Wishes
Milky Way Wishes Play through Milky Way Wishes
Original Kirby Movies Beat Helper to Hero with every helper
Revenge of Meta Knight Play through Revenge of Meta Knight
Revenge of the King Play through Revenge of the King
Spring Breeze Play through Spring Breeze
Staff Credits Complete Milky Way Wishes
To the Battlefield Play through Milky Way Wishes
Tomorrow's Wind Defeat King DeDeDe in Spring Breeze
Video 00 Complete Helper to Hero as all of the helpers
Video 31 Complete Meta Knightmare Ultra
Video 34 Complete The True Arena
Video 35 Complete 100 percent of the game