About 3/4 of them could be unlocked by simply watching the world record ones and seeing what bike they use and when they use their turbo. Doing so gave me 3 unlocked expert ghosts right there. One more and I'm getting Funky!

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0173-0974-1865 < Brawl friendcode!4253-4013-1847 < MKWii FC!
{Spur of the moment Toad Mario Kart poem below! lol it is bad!}