Kirby's Dream Land

Configuration mode:
Press Down + Select + B at the title screen. Options for the number of lives, sound test, and other selections will be accessible.

Hard mode:
Press Up + Select + A at the title screen. A special game with additional enemies and a new ending will begin.

Bonus game:
Hold Up + A + Select when the word "Start" appears at the title screen.

Hint: See Rick the Hamster:
Enable the "Hard mode" code and begin the game. When you get to the King DeDeDe level (level 5), you should see various doors with pictures on them. There are four different levels that you must complete before you can fight King DeDeDe. When you complete the first level by defeating the Boss at the end, it will seem as if the game freezes before you get back to the room. Press Up. Do this again with the second level, except this time pressing Right. Keep doing this in a clockwise order (in order from level one to level four: Up, Right, Down, Left) until you have completed all of the levels except for the King DeDeDe battle. When you defeat King DeDeDe and get to the screen where the different Kirbys are surrounding the main Kirby on a podium, you should see Rick the Hamster in the crowd of Kirbys.
Information in this section was contributed by Chroma.