Corporal Pig

Helmet Pigs (AKA Armor Pigs) are depicted as wearing stone helmets. They are the third strongest pig variety in the game, and serve as the chief enemy in the first set of levels in each theme. They're also seen serving as protectors to the King Pig and Mustache Pigs. Helmet Pigs are very much alike to Mustache Pigs in game ways, not actual looks. They have bosses, Herr Helmet, Hovering Helmet, Hardhat Hidalgo and Billy the Pig. Also, those bosses can also be achievements. The Helmet Pigs are approx. the same size as Medium Pigs. I assume they are Medium Pigs in stone hats. In old wikipedia Helmet Pigs were known as Soldier Pigs but the Soldier Pigs' name was reffered to as corrupt.