I have beaten some....but how do I unlock them?
In DS?
I think it's just beat all the other staff ghosts. :-\
Expert Staff Ghosts: You must beat the Nintendo Ghost on a stage. Like Moo Moo Meadows, you must beat the staff ghost by 5 seconds. In fact, for every Expert Staff Ghost, you must beat the Normal Staff Ghost by 5-10 seconds. I beat one. But you don't have to beat the Expert Staff Ghosts to unlock karts/characters.
Hope it helps.