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Nicole Richie couldn't stay composed during Thursday's 100th episode of Grey's Anatomy, as Izzie (Katherine Heigl) unexpectedly married Alex (Justin Chambers).

Richie took to her Twitter page after the show, writing: "Just watched Grey's & cried my f-ing eyes out."

The show definitely was emotional.

Meredith (Ellen Pompeo) and Derek (Patrick Dempsey) were supposed to wed -- and Izzie, who is battling a bran tumor, couldn't wait.

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Even though her hair was falling out and she was seeing visions of her dead ex Denny again, she was determined to fulfill her bridesmaid duties.

But after hearing news that Izzie was seeing Denny again, Derek performed an MRI and ended up finding a new, small (and inoperable) tumor.

Unable to help with the cancer, Meredith then handed over her wedding dress to Izzie, telling her that she should be the one wearing it.

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So Izzie ended up tying the knot in front of all Meredith and Dereks guests.

"Today's the day my life begins," Alex told Izzie in his vows. "Today I become a man, a husband. I become accountable to someone other than myself."

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They smooched, and Alex took her back to the hospital, where he shaved her head and told her she was beautiful.

The show ended with Izzie taking over the narration for Meredith and telling dead Deny to take a hike -- she was married to Alex now.

Tell Us: Do you think Izzie will survive?