How do you unlock red Yoshi in Mario kart wii?

All you need to do is beat the 100cc Special Cup to unlock your Mii. This means you need to win Gold on the 100cc Special Cup.All you need to do is beat the 100cc Special Cup to unlock your Mii. This means you need to win Gold on the 100cc Special Cup.

Additionally, you can unlock your Mii with different outfit by playing the time trials. Unlock 32 expert ghosts in the time trials to unlock Mii with "Outfit #2". So, you need to defeat a normal course ghost with a time at least seven seconds faster to unlock the expert ghost for that course. (Rinse and repeat 31 more times).