You still have to unlock mirror mode. 1-star rating in all CC's gives you golden wheels or something, not sure if other ratings unlock other stuff, I haven't bothered to check.
You can unlock all characters in 150cc by placing 1st in each cup, and unlock mii in 50cc, I'm not sure what you have to do though, I just got 3-stars in each cup in 50cc and my mii was unlocked.
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