In one of the dungeons, you will receive a hint that the enemy Pols Voice dislikes noise - yet blowing the whistle does nothing to hurt the enemy. The Famicom (the original Japanese version of the NES) had a microphone, and the player could make noise in it to kill these enemies. As the American NES aborted this feature, this was not possible. Nintendo went ahead and translated this hint verbatim, but because of the lack of a microphone in the American NES, it no longer made any sense and was often misinterpreted.
Some enemies fly using rotor blades, but each one only has one rotor blade, and it is impossible to fly with less than two.