Brown

Brown (ブラウン) is a robot in Mega Man 6 that mainly appears in Knight Man's stage. It resembles a barrel with a row of openings around the middle, and attacks by periodically firing an arcing projectile. The barrel is indestructible, but shooting it will cause the enemy to reveal its weak spot: the Met-like head contained within. The player must then shoot the head in order to defeat the enemy. Octone, an enemy from Mega Man 9,  behaves similarly. If Mega Man fires a Charge Shot from the Power Adapter, a Brown can be taken out in one hit without needing to expose the head first.