Izzie stumbled on her way down the aisle, but George stepped in and helped his old friend make it to the steps, where she exchanged vows with Alex. Tear.

Izzie and George in "What a Difference a Day Makes," from the fifth season of Grey's Anatomy. The emotional wedding scene was one for all time.

George and Izzie will always be close, even though their relationship has been through its ups and downs. What a wonderfully-written scene this was, when he helped her down the aisle.

Is George leaving Seattle Grace? This may be the photo of the long-awaited resignation.

Is George O'Malley as good as gone from Seattle Grace?

Is this the last shot of George O'Malley we will see on Grey's Anatomy? If so, he had a terrific run, and we will miss him dearly.

We now know who John Doe is, but didn't at the time.

George signs up for the Army, inspired by Hunt and by a patient named Charlie. But tragedy awaits him before he even ships out.

George decides he needs a purpose, and signs up for the Army. But little does he know, tragedy strikes.

Meredith finally learns the identity of John Doe. And it's shocking.

Meredith and John Doe (who we now know to be George) in the season five finale of Grey's Anatomy.

Or doing the best they can. George was a hero for what he did.