We've had to let go of some beloved characters during Grey's Anatomy Season 9, but we've also met some new ones. A lot of new ones, actually (*cough* interns *cough*). And it doesn't end with the characters we've already met.

What other new faces can you expect this season? We've gathered all the details about upcoming Seattle Grace-Mercy West newbies right here.

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Derek's sister: Neve Campbell will play Derek's (Patrick Dempsey) sis, Liz. She'll first appear in Season 9, Episode 8: “Love Turns You Upside Down” (airing December 6), and she has a multi-episode arc in which she butts heads with Meredith (Ellen Pompeo). Color us intrigued.

A New EMT: We can expect a new 30-something male EMT to show up for at least a three episode arc.

A new doc: Entourage's Constance Zimmer has been cast as Dr. Cahill, "a confident, self-possessed and laser-focused professional with a wicked sense of humor" who will appear in Episode 12-16. We know she has at least one scene with Arizona Robbins (Jessica Capshaw), and also appears in a big group scene.

A ... voice? There has also been a casting call for a male doctor in his late 40s who will appear in a three episode arc ... but we'll only hear his voice. Weird, right?

Are you excited for these new characters?

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Catch the next new episode of Grey’s Anatomy on Thursday, December 6 at 9 p.m. ET/PT on ABC.

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