Miis are the digital avatars that appear in the Mii Plaza from one of the Wii Channels. Miis are based off of human beings and players can design what their Miis look like so then the player can use them. Miis are playable characters in the game Mario Super Sluggers. Mii's can't be chosen as captains, they have 6/10 on all stats and chemistry to characters matching their colors, example. Red has chemistry with Mario and green has chemistry with Yoshi and pink for Birdo etc. It should also be noted that all male Miis are right-handed batters, while the female Miis are left-handed batters in this game.
Miis return in Mario & Sonic at the Olympic Winter Games. This time, Miis can be customized to wear different clothes and accessories. For example: a female Mii can use a Birdo Suit, or a Princess Peach suit. Unlike the last game, the stats differ depending on the gear.