Boss Endurance and Cake
     By  completing  the  game  you can unlock Boss Endurance mode for
Minigame and a Cake for your collection.

Boss Endurance: Complete the game once.
     Cake for collection: Complete the game once.

Time Attack Mode
     To  unlock  Time  Attack  mode  you  must  collect all 120 chests
throughout the game.

Hidden World
     To  gain  access  to  the  tower  in the center of the World Map,
collect  the  secret  map pieces from each of the other worlds. In the
tower, you can get any ability bubble, including the Triple Star Rod.

Hidden Birthday Message
     On  your  birthday,  play  the  game. After the startup sequence,
there will be a brief 'Happy Birthday!' message decorated with various
Kirby characters.

Get Special Abilities
     To get some special abilities, you need to do the following:

Fire Sword         Mix fire and sword (sword scroll needed)
Ghost              Get all of the pieces for the Ghost Medal 
                   and then beat the ghost mini boss 
                   (you will find him randomly instead of another 
                   mini boss). Then inhale him.
Ice Bomb           Mix ice and bomb (bomb scroll needed)
Ice Sword          Mix ice and sword (sword scroll needed)
Thunder Bomb       Mix lightning and bomb (bomb scroll needed)
Thunder Sword      Mix lightning and sword (sword scroll needed)
Triple Star        Beat the boss on area 8 (the one before 
                   the final boss), he will drop the Triple Star 
                   ability that you can use