Someone's apparently been hiding out at Seattle Grace all these years, Michael Ausiello of Entertainment Weekly reports, and we're guessing you didn't see this one coming:

It's Faye Dunaway!

Sources confirm that the Oscar winner (for Network), who hasn't taken a TV gig since a 2006 episode of CSI, has signed on for at least one episode of Grey's Anatomy.

That episode will air in February, and reports say she will play a renowned doctor at the hospital who crosses paths with the Chief, Cristina and Owen.

In other guest star news, Tyne Daly will be guest starring as Derek's mother this week, meeting Meredith for the first time in "Sympathy For the Devil."

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