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TV Line says that the former House star will play Anna.
Anna, who has a difficult past, moves to a small town in Maine where the magic of fairytales appears to be real.
Morrison played Allison Cameron in House and has a recurring role as Zoey in How I Met Your Mother.
Robert Carlyle, Ginnifer Goodwin and Lana Parrilla have also signed up for roles in Once Upon A Time.
