The head writer of last week's episode, Stacy McKee, talks about "Piece of My Heart" in great on the show's official writers' blog. Here's what she has to say about last Thursday's terrific Grey's Anatomy episode...

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Okay, before I start the blog, I have a confession to make. About the character of Addison: I love her. Not vagina monologue kind of love â€" but love nonetheless.

I love her sense of humor. I love her friendships with Callie and Bailey.

I love how Addison Montgomery has always known exactly how to call Derek out on exactly whatever it is he needs to be called out on.

I love how good she is at her job. I love that she's basically Sloan's McDreamy â€" even if his feelings aren't reciprocated. I love that she loves potato chips.

I love that she walks the hospital halls in heels that any normal woman would twist her ankle in... I love Addison. And I love that this was her Grey's Anatomy episode to come back to Seattle Grace for a visit.

The nice thing about bringing Addison back right now is that â€" she's been gone a while. She hasn't been privy to most of the Seattle Grace shenanigans since her departure.

So she's uniquely qualified to walk back through the doors at SGH and call things like she sees them. She can react the way we're all secretly reacting to Derek Christopher Shepherd pining away for someone OTHER than Meredith Grey.

She can notice just how much her good friend Callie seems to jive with newbie Erica Hahn… and Addison can get Bailey to admit (the way Bailey would NEVER admit to someone she saw and worked with everyday) that she is really struggling right now, just to keep it together.

Addison is a perfect sounding board because a lot of our characters don't have sounding boards of their own right now. Addison is a safe confidant. She can take in everyone's uncertainty, their panic, their pain… and take it right back to LA with her when she leaves.

No one needs to worry about their friends and colleagues at SGH seeing the cracks in their armor. Which is good. Because right now â€" there are a lot of cracks.

For instance, Izzie Stevens. She's floundering right now. She's all on her own and trying to figure things out for herself â€" but "on her own" is not exactly a comfortable place for Izzie to be…

She doesn't have the same kind of connection with George that she used to have; he's got Lexie now, and all of his other intern friends. Izzie's not at the top of her game professionally â€" she's not finding her medical stride like Meredith or Cristina.

Izzie's doing the opposite; she's hiding out in the clinic where even there her patients are requesting different doctors. Then there's Ava/Rebecca/Jane Doe. Izzie learns Rebecca isn't actually pregnant, but what can she do with that information?

As George and Lexie would say â€" she's coded. Hard.

Cristina's also starting to crack as Erica continues to shut her down over and over and over. The moment in surgery when Erica gives Alex props, and not Cristina â€" after Cristina is the one who massaged the baby's heart back to life â€" for me, that has always been a turning point for Cristina.

In that moment, I've always imagined that Cristina's world probably flashes before her eyesâ€" Cristina can't help but compare her relationship with Erica Hahn to how trusted and encouraged she always was with Burke.

The moment leaves Cristina a little raw, which is why she's able to confront Hahn later at the bar. But even when confronted, Erica's explanation to Cristina isn't exactly something Cristina can take a lot of comfort in…

Then there's Callie â€" and Erica.

And the vagina monologues, which â€" actually â€" I'm choosing not to blog about. This is one story you should just watch and enjoy. Anything I might say about it now will simply step on your enjoyment of what's to come, so…

Continue reading this writer's blog here ...

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