Caterina Scorsone

Private Practice has promoted Caterina Scorsone to series regular, TVGuide.com has learned exclusively.

"It's so fantastic for so many reasons," Scorsone, who plays Dr. Amelia Shepherd, sister to Grey's Anatomy's Derek (Patrick Dempsey), tells TVGuide.com of her promotion. "The set is really a wonderful environment. Everyone is generous and fantastic, so to know that's going to be my home for a while is pretty nice."

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Amelia was introduced late last season, when she clashed with the Oceanside Wellness docs over whether she could save one of their patient's lives. "She's very complex," says Scorsone, who actually went to medical school before deciding she'd rather play a doctor than be a doctor. "She inspires a whole rainbow of emotions in all the people around her. She's lovable and annoying at the same time," Scorsone says. "She's also tough and fragile at the same time."

Though she plays Derek's sister, Scorsone has yet to work with Dempsey, but is itching to do so. "It is a little bit intimidating, knowing how passionate people are, wanting to honor their expectations in the relationship with Derek, who is so deeply a part of people's emotional journey on this show."

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Executive producer Shonda Rhimes told TVGuide.com earlier this year that the writers were already discussing a Shepherd-centric crossover. "We've absolutely been talking about that," adds Scorsone. "Based on the history we've already established between Amelia and Derek, there definitely has to be some sort of encounter at some point."

As for the Season 4 premiere of Private, which the cast is currently shooting, Scorsone says the story will jump ahead a few weeks from Dell's death. "Everyone's had a little time to process and grieve," she says. 

What do you think of Scorsone joining the cast full time?