There’s a showdown in the town square this Sunday on Once Upon a Time (ABC, 8/7c), as wicked gets up in evil’s grill. And as that unfolds, viewers will gain some insight into the Wicked Witch’s tragic backstory.

“This weekend, we will find out what she wants and why she is green,” says series cocreator Eddy Kitsis. “We’re excited to show you ‘what her deal is,’ so to speak.”

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In recent weeks, Once has sprinkled around many Oz-some references, leading some to theorize that in the ABC series’ riff on the L. Frank Baum tales, courage-challenged Charming is the Cowardly Lion, and straw-spinning Rumple the addled Scarecrow. But, “There’s something to that, but something not,” responds cocreator Adam Horowitz. Adds Kitsis: “[Zelena] has a very interesting and complicated relationship with Rumple that you will be seeing this weekend.”

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TVLine also spoke with recurring player Rose McIver, who resurfaces Sunday as Tinker Bell, and she said that between the aforementioned Regina/Zelena face-off (“Bex Mader is doing a fantastic job as the witch, and that’s a very good scene to look forward to,” she teases), Neal’s “somber” funeral and other subplots, “You will see a whole collision of different emotions going on. Some bits are very suspenseful, some are very sad, some are hopeful.”

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Perhaps on the hopeful front, Regina will (somewhere) find time to touch base with Tink about having stumbled upon — and then fled from — her soul mate, Robin Hood aka The Man With the Lion Tattoo. “Tinker Bell understands that fear of promise,” McIver shares. “She has gone through that herself, believing that maybe she could have her wings back and then having that hope dashed [at first].

“But just because she understands, that doesn’t mean she agrees with orsupports the way Regina is handling things,” the Kiwi actress notes.

Surveying Regina’s strong reaction to spying Robin’s ink, EP Horowitz says, “The last thing she ever expected to see was to see that guy again. She put it out of her mind [back in Fairy Tale Land], and now all of a sudden she’s confronted with it, so she’s got to figure out how to handle it.” But at first, at least, “The easiest way for her to react is to run away,” says Kitsis.

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Currently filming the CW pilot iZombie, on which she stars, McIver says it was “exciting” to reprise Tinker Bell for this important beat in Regina’s love story. “That’s where our storyline began, with me telling her that he was going to be her soul mate. And now that she has bumped into him, it makes sense that Tinker Bell would be back in the middle of things.” Noting her skills as that rare beast of an actually winged wingman, McIver laughs, “Tink’s great that way — I feel like I need a Tinker Bell!”

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