Miis are customizable avatars that players can use in certain Nintendo games. The "Mii" feature is a feature on nintendo devices such as the 3DS, Wii, Wii U, and Nintendo Switch. On the 3DS (the device on which the Disney Magical World games are), there is an application called "Mii Maker" where the player can create customize many Miis. The player can have one main mii that they can use for certain apps and games that involve Miis or allow the Mii feature. They can switch out their main Mii for another Mii that they have created if they want to. There are certain apps that allow the player to involve several of their Miis including their main Mii.
In Disney Magical World and Disney Magical World 2, the player can either play as a self-created Mii from their Mii collection, or they can create an avatar using the Mii-inspired system provided by Disney Magical World. There are also many characters in Disney Magical World and Disney Magical World 2 with Mii like designs.
In the café, the staff (excluding the manager) can be customized either through the customization system of Disney Magical World OR the player can select a Mii which they have created. However, they can also just choose between male or female provided defaults.
In the KiraKira Shiny Star game, there is no choice of customizing the character as a Mii and instead, there is only the Disney Magical World customization. This is because it is an arcade game rather than a Nintendo game. More factors of customization and styles are added as the player progresses through the game.