How do you unlock sonic in Mario Kart wii?

You can't unlock Sonic in Mario Kart Wii. Sonic is a character from the *Sonic the Hedgehog* franchise, and he has never been in a *Mario Kart* game.

Mario Kart Wii has a variety of characters from the *Mario* universe, including:

* Mario

* Luigi

* Peach

* Bowser

* Yoshi

* Donkey Kong

* Toad

* Wario

* Waluigi

* Daisy

* Rosalina

* Baby Mario

* Baby Luigi

* Baby Peach

* Baby Donkey Kong

* Koopa Troopa

* Dry Bones

* Boo

* King Boo

* Toadette

* Diddy Kong

These characters can be unlocked by progressing through the game, completing challenges, or using unlock codes.