Do you want to build a really big snowman? When “Once Upon a Time” returns for season four, life will be more than a little chilly for the residents of Storybrooke. Not only will the show be introducing Disney’s newest royals, “Frozen’s” Elsa and Anna, but the town will have to handle the consequences of where the season ender left off. From the premiere outside the El Capitan in Hollywood Sunday night, the cast and creators teased the upcoming challenges for the fantasy drama.

“Emma’s in a very vulnerable state at this point,” said Jennifer Morrison. When we last left the savior, she had succumbed to her feelings for Captain Hook (Colin O’Donoghue) and had settled on remaining in Storybrooke with her family, something Morrison notes is a big step for the character. “She’s never really had a true home. There are all these relational things that she’s faced with and that’s really uncomfortable for Emma, she’s always been a bit emotionally stunted, so she’s definitely stretching and growing.”

Fans can expect Emma to be a little too busy to renew her dating life. “Obviously they have to deal with what happened,” added O’Donoghue, offering just a hint of a preview at how the “Frozen” queen is going to complicate things.

When we meet Elsa and Anna in the season opener, the sisters are grappling with an unsettling discovery about their parents’ tragic voyage that left them on their own in the animated flick. With a few clever, yet subtle, references to the mega-hit, the premiere sparks plenty of intrigue for the upcoming episodes, leaving viewers with several questions at the end of the hour, including the lingering mystery of how Elsa ended up in Rumplestiltskin’s vault.

“There’s certainly a relationship there,” said Robert Carlyle of how the imp will catch up with the sisters in Storybrooke. “He’s met them before – he’s certainly met Anna before,” he laughed.

But Rumple won’t be the only force Elsa will have to face when she arrives in Storybrooke, “confused and scared,” as Georgina Haig describes her. As “Once” viewers know – Regina (Lana Parrilla) hates newcomers. “She really does,” said Parrilla with a grin. “Anyone infiltrating her town, she has issues with.”

“Elsa shows up in her blue dress in Mary Margaret’s apartment,” said Ginnifer Goodwin, though the actress noted that Mary Margaret will not be directly involved with the “Frozen” story. “Mary Margaret is making things that happen with Regina and other characters not her business. She’s going to work on her own relationship with Regina,” a storyline Goodwin believes is going to make fans of the show happy.

Goodwin added that Mary Margaret will also find herself struggling once more with missing the life of one child. “[She] expected that having Prince Neal would sort of provide an emotional renewal… but instead has illuminated even more of the things she missed out on, not getting to raise Emma.” A former elementary school teacher in her cursed life, the character will also be thrust into a new job, “and she’s being expected to rule as she did in the Enchanted Forest.”

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

After spending season three kidnapped in Neverland and without a memory, Jared Gilmore noted that he’s looking forward to having a more active story when the show returns. “Henry’s going to have a great time,” said Gilmore. “He’s working with Mr. Gold, which is great. He’s my grandpa so we need some bonding time.”

Henry will also find himself working closely with Regina. “She’s on a hunt for someone that’s very secretive,” said Parrilla. “She’s definitely up to something and Henry sniffs it out. One thing I love is that she’s extremely forthright with him, and tells him exactly what she’s planning.” The Queen is nervous about how he’ll react, Parrilla said, though Henry is “totally into helping her!”

SEE ALSO: Jennifer Morrison Says Adding ‘Frozen’ to ‘Once Upon a Time’ Has Been Incredible

Cast members also teased the arrival of the Knave (Michael Socha) of the now-defunct “Once Upon a Time in Wonderland” spin-off. Though Socha could not comment on how he arrived in Storybrooke, he expressed his gratitude for being invited onto the series, and suggested that the Knave may find himself face-to-face with Robin Hood once more after violating the famous thief’s code back in Wonderland.

“It’s a safe bet, given our history that at some point we have to have a bit of a chat,” commented Sean Maguire, who plays Robin, who will also be forced to deal with the “very complicated” result of having his dead wife brought back from the past.

“This is a guy that’s built on honor and truthfulness and decency, and he has to honor his creed and his code but at the same time he’s fallen in love with somebody else,” he said. “It’s a complicated situation.”

The new season will also take a new look at the past, including a look at Prince Charming’s history, not delved into since season one. “We’re going to see a friendship that he had that in my mind is the most important he’s had outside of Snow,” said Josh Dallas. “[It] basically changes the whole direction of his life and sets him on the path of becoming a hero.”

Morrison remained mum on upcoming peeks into Emma’s past, and life in foster care, though the actress did tease that the story is “incredibly unexpected. What they reveal about part of her past is something that I didn’t see coming,” she admitted, “but I think it really adds a layer of depth to the storytelling that’s going to bring people even closer to the edge of their seats.”

Season 4 of “Once Upon a Time” premieres with new twists and intrigue, and an iconic Disney tune, at 8 p.m., Sept. 28 on ABC.

(Pictured: Jennifer Morrison and Colin O’Donoghue at the “Once Upon a Time” premiere party)