You have to unlock it in one of the tournaments i think....
Go on the Mii Channel on the Wii home Menu and edit your selected Miis size so that he is quite big and then go back on to Mario kart wii and look at your mii. He or she will be an adult mii.
I completed medals,mostly gold in all races. I now play as my mii..
Roselina
win 2,700 races
If you have a red outfit and you have Mii out fit B the outfit will be just like Mario's outfit.
You must win the Special Cup in 1st place under 100cc and then it should have your Mii in the character selection area.
you have to have gold in all the cups to unlock it :)
All you do is on the list of characters press the last one on the bottom.
to get mii outfit 2 you have to unlock all expert ghots on the time trials
A Mii is like a personal avatar that you use to represent yourself in some games. In wii sports, the Mii you choose will be the one you play as. In Mario Kart Wii, you can unlock "Mii Driver" which allows you to play as your mii in the races.
Get 15000 points on WIFI or do 3230 time trails. Its gonna be hard.
Mariokart wii
To get mirror cups in Mariokart Wii you willk have to complete all of the cups on all engune sizes
Put your mii in the mii parade.
You create a Mii then import into Wii Fit. Put in the age when you bring the Mii in and there you have it a baby for the Wii Fit.
Your mii can have two outfits-outfit A is fairly easy to unlock but outfit B is harder. Mii (Outfit A) - Win 100cc Special Cup Mii (Outfit B) - Unlock all Expert Staff Ghosts in all 32 Courses
On the Wii menu press A on the Mii Channel choose Start and choose New Mii play around with the various settings to create a Mii that represents you. Once your done save and quit and your mii will enter the mii plaza you can edit your mii here as well as delete them and put them in your Mii parade.