Instructions
Design a baby Mii in the Wii's Mii Channel. The look and design is completely up to you. Whatever you create here will appear in-game. Making your Mii short and on the rounder side will give it the look of a baby.
Unlock the ability to play as one of the Mii profiles stored on your Wii by getting a gold trophy on the 100cc Special Cup in "Mario Kart Wii."
Select your baby Mii as your racing profile in the main menu of the game.
Choose your baby Mii as your character from the character selection screen.