Ginnifer Goodwin knew she was in for a workout by signing on to play two characters on ABC’s “Once Upon a Time” — the virtuous Snow White and her real-world counterpart, elementary school teacher Mary Margaret.

But she didn’t know that by the end of the fairy-tale drama’s first season she’d be playing a third role, as aspects of Snow White and Mary Margaret’s personalities blur together when the stakes grow for the cursed residents of Storybrooke, Maine.

“It was a brand new kind of challenge for me to create what I think of as two sides of one coin,” Goodwin says.

Goodwin, a native of Memphis, Tenn., put her classical training with the Royal Shakespeare Company to work in bringing Snow White to life beyond the story book context that the audience knows all too well.

“It’s interesting to play characters that the public think of as being black and white. The challenge that we’re presented with is to make them gray, relatable and flawed,” she says. “I didn’t want Snow White to be the cliched fairy-tale princess, or a victim.”

Surprisingly, Goodwin found it tougher to nail the role of Mary Margaret. Once she got a handle on the rules that govern the twin worlds laid out by series creators and exec producers Edward Kitsis and Adam Horowitz, she began to find Mary Margaret’s center.

“I realized she couldn’t be a photographic negative of Snow White,” Goodwin says. “She had to have all the qualities of someone that the Evil Queen would want to watch suffer.”

Despite the unusual demands on the actors, Goodwin is grateful to be part of the “Once” ensemble. And she’s proud of the war wound she endured while lensing the third episode, when she suffered a deep cut above her eye and tore a ligament in her hand after colliding with a horse.

“I might have gotten hurt but it didn’t kill me,” she says. “I went straight back to work (after getting stitches) that day. I was afraid to sit around and feel sorry for myself. I wanted to get back to work because I loved the story so much.”