If you’re scratching your head and trying to figure out why the Wicked Witch (Rebecca Mader) is so green, you’re not alone. So far we’ve seen her at her greenest in Fairy Tale Land, confronting half-sister Regina (Lana Parrilla) atop the Evil Queen’s castle, but the two have yet to face off in Storybrooke — though that will change this week.

We’ve been promised an epic showdown in Season 3, Episode 16 (“It’s Not Easy Being Green”), but it sounds like we’ll also be getting some more intel on Zelena’s backstory, specifically learning why she turned out so… green.

“This week is the showdown,” co-executive producer Eddy Kitsis teased to TV Guide. “We will find out why the witch is green and what she really wants.”

We already know that the Wicked Witch is jealous and envious, so perhaps she is literally green with envy? That would be a very simple answer, but we hope that maybe we’ll learn that it has something to do with Glinda being cast. The synopsis does say we’ll get to see the WW in Oz, so at least we know we’ll get to visit yet another magical land.

Either way, Zelena is proving to be the “big part” for the season that she was promised to portray, and we’re loving every minute of it.

Why do you think the Wicked Witch is green? Hit the comments and speculate before this Sunday’s episode!

Once Upon a Time airs Sunday nights at 8 p.m. ET on ABC.

Carson Blackwelder is an Associate Editor at Wetpaint Entertainment. Follow him on Twitter and Google+!