Since the Grey's Anatomy cast was away from the set for months, some of her co-stars use this opportunity to congratulate Katherine on her big-screen success.

Justin Chambers, the actor who plays Katherine's former flame Dr. Alex Karev on the show, shares what it's like to act alongside this "it" girl. "Katherine Heigl, you rock," he says. "You are a gifted actress, and I am very happy that we get to work together."

Katherine may be blessed with movie-star looks, but according to Justin, she's just as beautiful on the inside. "I laugh thinking about her," he says. "She burps like a truck driver, for such a lovely lady, which is kind of cool. And she always says, 'Excuse me' after she burps, which is even cooler. She's got a big, big heart, and she's very talented. I learn from watching her."

T.R. Knight isn't just Katherine's co-star—he's such a close friend, Josh asked him to be a groomsman in their wedding. As a special surprise, T.R. penned a song for his friend, Katie.

Watch Watch T.R.'s musical tribute to Katherine.

In the song, T.R. sings, "It's all about how you're the awesomest of dames. And you're a great friend, a friend to the end. You're there without fail. We're like Oprah and Gayle!"