For the cast of “Once Upon a Time” bringing new life to classic characters is a gift that keeps on giving. The cast of the fairytale drama took to the carpet at the show’s season four premiere Sunday at the El Capitan, and talked about what it’s like to continue adding to classic but evolving mythology.

“As an actor it’s all you want,” exclaimed Rebecca Mader, who stared in the back half of season three as the Wicked Witch Zelena, out for vengeance against half-sister Regina. “You get the chance to show all the dimensions – the reasons why a character’s become what they’ve become. I love that they gave that to Zelena.”

As opposed to making villains on the series strictly the big bad, “Once Upon a Time’s” writers have developed a reputation for showing something more recognizable in the backstories of their characters, heroes and villains alike. “It’s what makes TV and film interesting,” said Mader, “when you take a villainous character and add dimensions it’s just delicious,” she said, noting that the joy is in developing arcs that viewers can care about and become invested in.

SEE ALSO: ‘Once Upon a Time’ Showrunners Talk ‘Frozen,’ the Charming Family’s Challenges and Regina’s Evolution

Coming up, viewers can expect to see the return of “Frozen’s” villain, Prince Hans, played by Tyler Jacob Moore. The storyline will resume almost immediately from where the animated film left off, with Hans kicked out of Arendelle and sent back to his 12 brothers, who, as Moore said, “are not going to be too happy with him and what he’s done.”

Moore added that while his character is only seen as a bad guy, thus far, is “Once” storyline will get a “reasoning behind the madness. I think they’re doing a good job of giving the audience little hints and teases of why Prince Hans would do this.” The actor exclaimed that he was previously a part of the anti-Hans camp with fans of the film, though now that he gets to portray the character he’s realizing the importance of adding to the stories, a situation that comes with a certain expected pressure.

“Nothing quite prepares you for people screaming out ‘Let It Go,’” laughed Georgina Haig, who is joining the cast as Elsa. Haig walked the carpet with Elizabeth Lail, who plays younger sister Anna in her first on-screen appearance. The two noted that they’re “excited but nervous” about reviving the characters after their box-office-busting debut last November, and are looking forward to building on the stories audiences have already fallen in love with.

“There is pressure,” Haig said, “because the Elsa/Anna story has really hit a nerve with people in a way that is kind of sacred. The spirit of that very much follows through into ‘Once Upon a Time,’” the actresses shared before a screening of the premiere episode that introduces the sisters to the “Once” story, through a mystery unaddressed in the film.

“That’s the fun for us,” said series creator Adam Horowitz. “What we’re doing is taking those characters and throwing them into the mix of what we’ve been doing for three seasons, and we think it scrambles up the playing field in a fun way.”

“I think that’s everything, really,” added JoAnna Garcia Swisher, the show’s Ariel. “What makes the show unique is having the backstories and the original charm and glamor, mixed with all these fresh ideas.”

“Adding ‘Frozen’ to the show has been incredible,’ said Jennifer Morrison, who will be spending screen time with Haig as Emma and Elsa bond over learning how to control their respective magic. “[The writers] do such a wonderful job of adding layers to these stories that we’ve known for years and now we’re doing it with a fresher fairytale.”

Season four of “Once Upon a Time” premieres at 8 p.m. Sept. 28 on ABC.

(Pictured: Ginnifer Goodwin, JoAnna Garcia Swisher, Elizabeth Lail and Georgina Haig at the premiere of “Once Upon a Time”)