Guest stars Roger Rees (Dr. Marlow) and Elisabeth Moss (Nina Rogerson) previously worked together on the NBC drama, The West Wing.

Ratings: 22.3 million viewers

Meredith: (voiceover) Surgeons always have a plan. Where to cut, where to clamp, where to stitch. But, even with the best plans complications can arise, things can go wrong. And suddenly you're caught with your pants down.

Meredith: (closing voiceover) The thing about plans is they don't take into account the unexpected, so when we're thrown a curve ball, whether it's in the O.R. or in life, we have to improvise. Of course, some of us are better at it than others. Some of us just have to move on to plan B, and make the best of it. And sometimes what we want is exactly what we need. But sometimes, sometimes what we need is a new plan.

George: Izzie.
Izzie: George.
George: What the hell happened last night? Did I at least call Callie before I passed out?

George: I was drunk, I'm sure I didn't mean whatever I said or did.
Izzie: Yes George, you meant it. You meant it many times.

Addison: So, God wants you to be an adulterer?
Izzie: Well, God got a virgin pregnant by magic. He’s not playing by the rules.

Cristina: Nobody, meaning me, needs to hear George's rendition of "Sexyback" at 3 in the morning.

Meredith: I let Mark use the memory of my mother to win points with the Chief. You were right.
Derek: I'm sorry.
Meredith: Your know what's weird?
Derek: What's weird?
Meredith: It's exactly what she would have wanted.
Derek: Dead mommy's proud?
Meredith: Dead mommy's proud. How was your interview?
Derek: Not great. It wasn't great. I was distracted.
Meredith: By what?
Derek: Nothing. I don't know.
Meredith: On a scale of 1 to 10 how bad is it?
Derek: Eight.
(Meredith kisses Derek)
Meredith: How about now?
Derek: Seven.
(they kiss again)
Meredith: How about now?
Derek: Six.
(they continue to kiss)
Derek: Five, four, three...

(Alex is helping Jane Doe choose her new face)
Alex: Lets meet the contenders. Lets see. This is, this is Maggie. Married a high school sweetheart and has two kids. Loves being a mum. Coaches her daughters basketball-team. And makes an insane banana cream pie. And This is Elizabeth. Graduated from Northwestern . Met her husband at a political rally where they got arrested and fell in love. She's all angry and fired up, but everyone forgives her cause she means well. This, one, this one is Eva. She's funny, she's tough and a little neurotic sometimes, but you get used to it. You can tell she's been through a lot in her life, but it only made her stronger you know.

Episode Title: My Favorite Mistake

"My Favorite Mistake" is the title of a song performed by Sheryl Crow.

Cristina: Nobody, meaning me, needs to hear George's rendition of "Sexyback" at 3 in the morning.

"SexyBack" is the title of a hit song by Justin Timberlake.