Below are three more sneak previews of the 100th episode of Grey's Anatomy Thursday, "What a Difference a Day Makes." In the first, Mark and Meredith talk about the wedding in mid-surgery. Sloan "warns" her that he doesn't want to be Derek's best man a third time ...

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Follow the jump for two more clips from the episode that have nothing to do with the wedding, but do show George O'Malley in action as a trauma patient is rushed to the ER ...

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Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.