Former Chicago Hope, Ally McBeal, Numb3rs and 24 star Peter MacNicol has joined the cast of Grey's Anatomy for a multi-episode arc this season, TV Guide reports.

The actor will play Dr. Stark, a pediatrics attending who will be working closely with Alex (Justin Chambers), and presumably Arizona (Jessica Capshaw) as well.

MacNicol will pop in during November sweeps for at least two episodes, so you know the role is significant. Any thoughts on what the upcoming plot line might be?

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