Mii

A Mii is a digital avatar that represents the player in various games. It is used on the Wii, the 3DS, and the Wii U.

Nintendo Wii
It is created using the Mii Channel on the Wii, and can be used as the player in multiple Wii games, most notably in Wii Sports, to represent the player, and the Miis can also be moved from system to system by downloading them, or by saving them on the Wii Remote and placing a copy on another Wii.

In, in addition to modifing your basic face, the player can go to The Shampoodle Salon and can buy a mask in the shape of a Mii's face for 3000 Bells but the first time you do this, it will be free.

To remove the mask, just remove it the same as you would remove any accessory. If the player gets any bee stings, they will not be visible, but other villagers will still act like they are still there. Any hats and other accessories will be removed when the mii mask is worn.

Nintendo 3DS
Miis once again appear on the 3DS, appearing first in Pilot Wings Resort. It is unknown if they will have the same role in as they did in City Folk.