Disney now owns the rights to the Star Wars franchise and also owns TV network ABC, which airs Once on Sunday nights.
"When Disney bought Star Wars, my first thought was, 'When's C-3PO coming on?'" Sbarge - who plays Archie - told Entertainment Weekly.
However, Sbarge added that the Once Upon a Time writing team would have to maintain the show's "integrity" if they were to have Star Wars characters into the series.
"It's above my pay grade, but I would imagine there's a fine line for [the writers] to walk," he said. "Part of what makes this show work is even though they have broken the rules in one sense, they have a lot of structure to what it is they've laid out.
"If they do bring a Star Wars character, I'm not sure how they do it, but I imagine they'd do what they have done, which is figure out a way to make sense of it. While they can go anywhere, they've created a rulebook we all follow and that's given [the show] its integrity."
Star Wars rare behind-the-scenes pictures - photo gallery:Robin Hood and Tarzan could "absolutely" appear on the show, while Mary Poppins was also "in-bounds".
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Watch a promo for Once Upon a Time's winter finale below: