In world 3: Butter building, at Level 1. Fight the clock that gives you microphones, Use 2 of the microphones but let 1 microphone remaining. Find the button to open the 1st secret, now comes the hard part. Jump onto the button while you use your last microphone! If done right, Kirby will have unlimited microphones. Note: you lose the power if you fall
into a gap, or get hurt by an enemy.