'Once Upon a Time' has Anna and Elsa of 'Frozen'

Kristoff, voiced by Jonathan Groff, left, and Anna, voiced by Kristen Bell, in a scene from Walt Disney Pictures' 'Frozen'

SAN DIEGO -- Anna and Elsa of "Frozen" have arrived in Storybrooke.

At Saturday's "Once Upon a Time" panel at Comic-Con, producers played a clip from the season 4 premiere revealing characters from the Disney movie.

In the scene, sisters Anna and Elsa (portrayed by Elizabeth Lail and Georgina Haig) put flowers on their parents' graves. Elsa tells Anna she has a surprise planned for her wedding.

Elsa and Anna's "Once Upon a Time" story picks up after the film.

"Frozen" characters Kristoff and Prince Hans will also be introduced.

Producers also showed a video poking fun at incorporating "Frozen" into the series.

In the spoof, the writers, along with creators Adam Horowitz and Edward Kitsis, brainstorm ideas for season 4. They say things like, "We've done a lot of Disney villains and we're running out" and "We're consuming witches 85% faster than we can create them." A pizza delivery guy shows up and suggests they take on "Frozen."

Cast members including Jennifer Morrison, Lana Parrilla, Robert Carlyle and Josh Dallas were at the panel.

Dallas' wife, co-star Ginnifer Goodwin, was not there. She taped a video saying hello from the set. In real life, Goodwin and Dallas are married with a newborn son.

Dallas described fatherhood as "the greatest thing that's ever happened" and called the baby his soul mate.