Once Upon a Time is set to bring a few familiar faces to your screen this fall, but who are they leaving out and what intentions do they have for Elsa and company?

Ahead of Comic Con, where ABC’s Once Upon a Time will hold a panel on Saturday, July 26, Adam Horowitz and Edward Kitsis dished some details about their “expensive fan-fiction” Frozen crossover.

In an interview with EW, Horowitz and Kitsis discuss their intentions for sisters Anna and Elsa, and reveal a heartbreaking casting decision. Olaf will not make an appearance in Once Upon a Time‘s Frozen journey. Deciding his story was best left as is, what other story lines are the creators staying away from?

Elsa, our misunderstood heroine, will once again explore the world of Storybrooke looking for the love that comes from family and acceptance. Without her sister around, at least initially, Elsa is once again surrounded by those who do no understand her powers or the damage that they can do when she loses control. The Once Upon a Time writers room is not interested in mapping out a dating profile for Elsa. Hororwitz says, “We’re more interested in what the movie explored, the relationship between sisters, and that relationship will be central to the story.”

Season 4 will follow the same trajectory as season 3, with the first half of the season focusing on the Frozen storyline and the second half on an unannounced arc. The creators were very clear that anything they write into Once Upon a Time is isolated from the work that Disney may be putting into Frozen 2. Horowtiz describes Once as, “a Disney cul de sac, you can come in, and have some fun with the characters, leave, and the characters are what you loved before.”

There are exceptions to every story, of course. In the case of last season, the twist on Peter Pan’s past turned his shadow from a playful nuisance, to an evil ethereal creature voiced by Marilyn Manson. This season will introduce a new character to the Arendelle universe played by Elizabeth Mitchell. Horowitz and Kitsis did not reveal her role in detail, but narrowed it down to the original Snow Queen, or perhaps Anna and Elsa’s mom survived the ship wreck.

Speculate away!

Last week, Adam Horowitz tweeted that filming had begun on the soundstage where Arendelle will be brought to life, and that a certain reindeer made an appearance. While Olaf may be out, Sven, Kristoff’s trusty side kick returns!

One other item of note, there will be no signs of singing in Arendelle or Storybrooke. Many of you may rejoice, but for those who were hopeful for a musical episode, switch on a Disney shuffle and remember it is going to be alright.

In case you missed it, check out the photos of Elsa’s first appearance in Storybrooke.

Let us know what you think of the Frozen story arc!

Once Upon a Time returns Sunday, September 28 at 8:00 p.m. on ABC