Grey's Anatomy by Randy Holmes/ABC Grey's Anatomy by Randy Holmes/ABC

Viewers weren't the only ones surprised by the Grey's Anatomy finale shocker on Thursday. No, Shonda Rhimes wrote Friday in her blog that she kept the Mer-in-a-pool-of-blood secret from the show's other writers, up until the very last moment she could.

The reason behind Rhimes' long wait is that, she explained, she starts with the last scene of her finales before stepping back to plan out what comes before it. Yes, that means that she's pitching the end of Season 5 Friday (!), and that Thursday's big finale underpinnings were actually hatched four years ago. For Rhimes, though, the big moment was not in the kiss, but in the moments after.

"For this season," she explains, "I knew immediately that I wanted more hope. I knew I personally NEEDED more hope. So I pitched Meredith standing on Derek's land in a field of candles telling Derek where the living room could be, where the kitchen could be, where the kids could play. Because I wanted them together."

The trick for Rhimes, though, was getting Mer there, and the key, she realized, was in what Ellis Grey told her as she lay dying: Be extraordinary. Not in surgery - but in love. "[That] made it possible for Mer to stand in a field of candles because once she realizes that, her whole world opens up," Rhimes writes. "She can just stand there in her joy."

And as for Callie, Erica and Mark? Rhimes promises that, while Sloan won't become anyone's hero, per se, there's some more evolution in store for a complicated story. "You'll be very surprised when you find out where this story is heading next season," she said. "Because we don't do things the easy way. And none of this will be easy."

Of course, don't expect anything too warm and fuzzy. That, Rhimes reminds us, is what makes it Grey's Anatomy. What could she be thinking up for this time, next year? Sadly, we're all going to have to wait. - Anna Dimond

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