ABC's Once Upon a Time has teased an exchange between the two popular Frozen sisters Elsa and Anna for the upcoming fourth season of the series.

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There will be a Frozen invasion on Once Upon a Time this fall as characters from the popular animated film are introduced. The Once Upon a Time Twitter account tweeted a photo of a script from the first episode of the season on Sunday, featuring Elsa (Georgina Haig) and Anna (Elizabeth Lail).

"Now come on. I have a surprise for you," Elsa says, followed by Anna's quippy response: "Really? Because surprises tended to be hit or miss in this family."

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This seems to be a clever reference to Frozen, which features Elsa revealing her icy powers in the beginning of the film to a rather un-accepting Arendelle.

The tweet also features the hashtag "#OnceisFrozen," suggesting that the series will be heavily featuring the popular movie's characters.

Other Frozen characters set to appear in the upcoming fourth season of Once Upon a Time include Kristoff (Scott Michael Foster), Hans (Tyler Jacob Moore) and Pabbie the elder troll (voiced by John Rhys-Davies).

The premiere episode of the season is titled A Tale of Two Sisters, indicating that the series will be delving into Elsa and Anna's relationship right away when it returns for Season 4. Each of the Frozen characters will be recurring in the first half of the season.

Once Upon a Time Season 4 is set to premiere Sunday, Sept. 28 at 8 p.m. on ABC.

Tags: Once Upon A Time television ABC