One of the show runners of Once Upon a Time has revealed the title of the first episode of Season 4, and in case there was any doubt that Frozen wasn't going to be a main story arc, the title will end the speculation.

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The Season 4 premiere episode for Once Upon a Time is titled A Tale of Two Sisters, according to a tweet Monday by OUAT co-creator and show runner Adam Horowitz.

"Here's our first #OnceUponATime #titlespoiler of season 4 -- hope to see ya this fall!" he tweeted alongside the photo of the first script, with the title featured in plain view.

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Considering all the hype surrounding three characters from Frozen appearing in Season 4 of the series, it seems very likely that the "two sisters" refers to Elsa and Anna. The premiere episode is written by Horowitz and fellow co-creator Edward Kitsis.

Elsa made her first appearance on Once Upon a Time in the Season 3 finale, with the audience only seeing her from the back, though fans immediately recognized her iconic blue dress and blond braid and attributed it to Elsa.

The casting for Elsa, Anna and fellow Frozen character Kristoff was announced recently. Elsa will be played by Fringe actress Georgina Haig while Anna will be played by newcomer Elizabeth Lail and Kristoff will be played by Scott Michael Foster (Greek).

Elsa will appear in nine episodes of the upcoming season, Anna will appear in between six and eight while Kristoff will appear in as many as six. Presumably this will all be in the first half of the season but this has not been confirmed.

Once Upon a Time Season 4 debuts in the fall on ABC, though the network has not yet announced a set air date. It will be returning to its regular Sundays at 8 p.m. timeslot.

Tags: Once Upon A Time television ABC