1) They must have beaten at least two higher-seeded teams in the tournament.As you see, unless Duke or Syracuse gets beat tonight, the first time a "Cinderella" could potentially be named would be on Saturday. Even then, I would hesitate to name Washington as a Cinderella if they beat New Mexico, since I think that beating a team from the Mountain West Conference shouldn't really count.
2) The only exception to Rule 1) is if a 16 seed ever beats a 1 seed.
How 'bout that Big East? Isn't it cute when people think that conference is supposedly the best in basketball? They're so funny...
Update 1327 20 March: OK, so St. Mary's now qualifies as a "Cinderella", but let's face it -- it appears that beating a "Big Least" team this year isn't really that much of a surprise...