Once Upon a Time season 4 sees the Frozen characters join the fray. One of the most interesting combinations will be Elsa and Emma’s unexpected friendship.

In last Sunday’s Once Upon a Time season 4 premiere, we were introduced to Elsa (Georgina Haig), Anna (Elizabeth Lail) and Kristoff (Scott Michael Foster) from last year’s smash hit Frozen.

Related: Once Upon a Time season 4, episode 2 sneak peek: Elsa seals off Storybrooke

TV Line has posted a lengthy interview with Jennifer Morrison (Emma), in which she previews episode 2. As seen in the promo, Elsa accidentally traps herself and Emma in an ice cave — and surprisingly, this experience forms a bond between them (even while Emma is slowly freezing to death).

“The crisis in the ice cave, combined with the many similarities that they share, makes Elsa and Emma fast friends,” Morrison says. “Emma realizes quite quickly that Elsa is misunderstood and is just trying to get her sister back and get her powers under control.”

Morrison also reveals that Elsa will help Emma learn how to focus her own magic, which she is still learning how to use.

Related: New Once Upon a Time season 4 images reveal Elizabeth Mitchell’s Snow Queen

She goes on to discuss Emma’s relationship with Regina, and teases an upcoming episode which will focus on the conflict between them.

“They start dealing with how complicated [their] situation is,” Morrison explains. “It’s not like they ‘duke it out,’ and it’s not like they talk it out, but they start dealing with it.”

Finally, Morrison reveals that future Emma flashbacks will throw “a bit of a curveball […] that I didn’t see coming.” We wonder what surprises can possibly be left in Emma’s backstory! But it’s Once Upon a Time; there’s always going to be new stories to tell.

Watch the promo for episode 2 below:

Once Upon a Time season 4, episode 2, “White Out,” airs this Sunday at 8/7c.