Minoan

Minoan (ミノーン), also known as Fan Blade, is an enemy in Mega Man 4. They appear in Bright Man's stage, the second Dr. Cossack stage, and the third Dr. Wily stage, among other areas. They stay up on a mount in the ceiling, and while hanging, the Minoan is invincible to all weapons. If Mega Man gets close or the mount it hangs in is destroyed, the Minoan will then drop down, open up, and spin toward him. Interestingly, not only are Minoans invincible to Dive Missile, the Special Weapon is unable to home in on it. Rain Flush can take it out with ease.

Hits Data Chart
Amount of shots/hits from Special Weapons it takes to destroy a Minoan.

Trivia

 * Minoan's name is derived from the Japanese word "minomushi", which means bagworm.
 * It is blue in its official artwork while its game sprite is green and yellow.