Your Mii can be a playable character in Mario Kart Wii! To use your Mii, first ensure it's created and saved on your Wii console. From the character selection screen, navigate to the Mii icon. You can then choose from any Mii stored on your system. Miis are categorized into weight classes (Light, Medium, Heavy) based on their size, which affects their kart/bike selection and stats. A smaller Mii will be a Light character, while a larger Mii will be Heavy. Selecting a Mii allows for a personalized racing experience, letting you race as yourself or your friends against the Mushroom Kingdom's finest.
