Kirby's Adventure

Bonus games:
Successfully complete the game and save the game. An option to play the bonus games will appear when selecting that saved game from the title screen.

Extra Game:
Successfully complete the game with a 100% rating.

Sound test:
Successfully complete the "Extra Game".

In-game reset:
Press A + B + Select + Start during game play.

Unlimited Mikes:
Defeat the Boss, then use the last Mike to hit the bonus plunger or piece of the star rod.

Just before you hit a star pad (the pad that reveals some secret level, warp, game,etc.), play the third song on your Mike. If done correctly the screen will glitch for a split second and you will have unlimited Mike usage.
Information in this section was contributed by starjack.

Hidden initials:
In world 1 level 2, grab any power and find the Warp Star. Walk away from it so it is just out of sight, then release your power with Select. The warp star will be gone and you can walk to the end of the level, where "HAL" will appear.
Information in this section was contributed by jeeee.

Alternate ending:
Successfully complete the regular game to view the ending credits. Then, defeat all of the Bosses in the "Vs. Boss" option at the "Bonus Games" screen. It will be the same ending, except Kirby will keep making mistakes.
Information in this section was contributed by Tim Owens.

Hint: Hi-Jump:
Use HI-Jump and aim your jump at a monster. It will be killed when you hit it, and you will not be hurt.
Information in this section was contributed by Monkeyman.

Glitch: Yellow Kirby:
Go to a Warp Star Station in any level with the Fireball power. Use the Fireball power to dash onto a star. Kirby will become yellow until he crashes to the ground on a star.
Information in this section was contributed by Chriz Horte.