Patrick Dempsey, Caterina Scorsone

If you haven't yet heard, Grey's Anatomy and Private Practice are doing another crossover this season, and TVGuide.com has the exclusive details on who's popping up where.

Exclusive: Grey's Anatomy and Private Practice doing another crossover

As we first reported, Private's Amelia Shepherd (Caterina Scorsone) will venture up to Seattle Grace in the first hour of the crossover during Grey's. She'll plead with older brother Derek (Patrick Dempsey) and sister-in-law Lexie (Chyler Leigh) to help save the life of Erica (A.J. Langer), who, it was revealed in Thursday's episode of Private, is suffering from a serious ailment.

Next, Derek and Lexie are scheduled to appear in the Private hour of the crossover, but in a surprising twist, they won't be heading to Seaside Wellness. Instead, they'll stay put, and Cooper (Paul Adelstein), Charlotte (Kadee Strickland) and Erica's son Mason (Griffin Gluck) will make their way to Seattle Grace, which will become Ground Zero in the rush to save Erica.

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The special crossover episodes of Grey's Anatomy and Private Practice are slated to air Thursday, Feb. 16 beginning at 9/8c on ABC. Private Practice, which has regularly followed Grey's, will move to Tuesday nights at 10/9c once executive producer Shonda Rhimes' third drama Scandal debuts on Thursday, April 5 at 10/9c.