Defeat King Dedede to replay any desired level.
Collect all Red Stars to unlock hard mode.
Collect all Red Stars in hard mode to unlock some secrets. The sky changes pink, there are Kirbies you can control in the opening scene, and a free-play mode will be available for mini-games.
When you start level 4-3, you will see four Waddle-Dees walking around in a circle. Flip them and they will turn into blue stars. Collect all four of them to earn a life. Repeat this as many times as needed to collect an unlimited number of lives.
Set up a red bumper exactly vertical or horizontal with the bumper. Repeatedly roll into the bumper to become temporarily invincible.
Use the blue glove power-up to get pushed in the air three times consecutively to become temporarily invincible.
Enter a jumper, then jump out of it and into another jumper. Immediately jump out again into another jumper. Jump out once more time to become temporarily invincible.