Once Upon a Time: Zelena Faces Dorothy and the Scarecrow In this scene from the April 3rd episode of Once, Zelena is in Oz and is threatening the Scarecrow... until Dorothy shows up.
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In Oz, many years ago, Zelena tries to make a time travel spell by using the Scarecrow’s brain but Dorothy comes back to Oz and foils her plans. Hades shows up offering help but she turns him down.