ABC's hit American fairy tale drama Once Upon a Time, shocked fans in its Season 3 finale with the unexpected appearance of Elsa from Disney's animated film Frozen. Executive producer Adam Horowitz revealed that the character will appear in at least nine episodes set in Storybrooke. The next installment of the series, Season 4, has announced open casting.

Casting for the upcoming season is set to find actors for other Frozen characters besides Elsa, such as Anna and Olaf. On his June 13 tweet, Horowitz confirmed the show's return sometime in the last quarter of the year. "Casting for #OnceUponATime Season 4!  Hard at work! Hope to see ya this fall!"

Horowitz added that the inclusion of the familiar Frozen characters next season will remain on the animated side and no further alterations will take place. "But what we are going to do, we're not ready to tell you. But what we can say is we're very aware of what we think makes this character from Frozen so special and we want to honor that and make sure that what we do is in the universe of (what) everyone fell in love with this past year," he told E! News.

Options for Elsa's actor have not been finalized yet, but the show is keen on giving the offer to Idina Menzel, who is the voice behind the role in the Disney film. Similarly, internet sensation Anna Faith Carlson is also eyeing to portray the role, according to her social media posts of her dressed as Elsa.

The 18-year-old wrote this caption on Instagram, "I know this is kinda a lot to ask, but it would mean the world to me. Can you take a picture from my page dressed as Elsa, post it and hashtag the words #AnnaAsElsa? I'm hoping to audition as Elsa on 'Once Upon A Time'! You can do it on Instagram and/or Twitter. :) THANK YOU SO MUCH!"

Once Upon a Time, Season 4, is slated to release in September, 2014.