Sandra Oh, Ellen Pompeo Sandra Oh, Ellen Pompeo

As Grey's Anatomy winds toward its Season 8 finale, the major question is not only which actors will return next season, but also which residents will actually pass the medical boards in order to become full-fledged doctors — and hopefully, continue walking the halls of Seattle Grace.

"You're going to see how each person deals with [the boards]," creator Shonda Rhimes tells "How some of them rise to the occasion, how some of them crack, and some of the problems they're going to be facing."

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While the residents are off taking their boards, the attendings will have problems of their own. "Teddy and Owen still have issues to work out, and we have a lovely Callie-Arizona [Sara Ramirez and Jessica Capshaw] story coming up," Rhimes says. "There's going to be some definite surprises in store for the Chief [James Pickens Jr.] and Catherine Avery [Debbie Allen], Jackson's mom." Plus: Loretta Devine will reprise her role once again as the Chief's Alzheimer's stricken wife Adele. "That's going to be beautiful," Rhimes says.

With the fate of many Seattle Grace doctors up in the air, Rhimes is finding it extra difficult to map out the season finale. "There's a sense of nostalgia there that's really big in terms of these interns no longer being residents anymore," she says. "That alone is a big deal for us. It's also just difficult in terms of what we're trying to do in this finale. What we're trying to do is pretty large and the idea that we're pulling things apart and putting things back together in this very interesting way is not easy."

One thing Rhimes can promise: The hospital will live to see another day. "I'm not going to blow up Seattle Grace," she says.

Grey's Anatomy returns Thursday at 9/8c on ABC, followed by the series premiere of Rhimes' new drama Scandal.