Miis first appeared as custom avatars for the Nintendo Wii console. They've since served similar purposes in many Nintendo games, and have now debuted in Super Smash Bros. as fighters!
There are three different types of Mii Fighters: the Mii Brawler, the Mii Swordsman, and the Mii Gunner. Each different type of Mii Fighter has their own unique moveset, along with 12 different customizable Special Moves. Their speed and power are affected by their height and weight assigned by the Mii Maker. Keep in mind that Mii Fighters cannot be used online with strangers.