"Once Upon A Time" season 4 spoilers already revealed the title for the first episode when the series resumes airing on September 28.

Co-creator Adam Horowitz revealed "Once Upon A Time" season 4 spoilers on Twitter when he wrote that episode 1 will carry the title "A Tale of Two Sisters," which could refer to Queen Elsa and Princess Ana if the series will follow the "Frozen" story arc.

Then Adam Horowitz uploaded an image showing episode 2 with the title "White Out," along with the caption: "Here's another #OnceUponATime #titlespoiler Hope to see ya 9/28 for Season 4!"

Those who watched "Frozen" may surmise that this would be the time when Queen Elsa in a moment of panic unleashed eternal winter in the kingdom. Earlier "Once Upon A Time" season 4 spoilers revealed that it would be "Ice vs. Ice" or Queen Elsa against the Ice Queen in the "Frozen" crossover.

According to Inquistr, there's a theory that OUAT will tweak the story to make it appear that Queen Elsa's mother is still alive even if she presumably died in "Frozen." She could be saved by the mermaid Ariel when she saw the shipwreck.

Writer Edward Kitsis confirmed to Entertainment Weekly that "Elizabeth Mitchell's character is connected both to the world of Arendelle and the world of Storybrooke." Inquistr also reported that, based on the previous report by EW, Elizabeth Mitchell's character might be the "malevolent" Snow Queen which could set up an Ice vs. Ice battle with Queen Elsa.

The E! News revealed "Once Upon A Time" season 4 spoilers when it reported that Prince Hans-like character will have a recurring role when the series resumes. The character is described as "refined and well-spoken on the outside, but he has a serious chip on his shoulder and an even more serious mean streak."

Those who watched "Frozen" will recognize Prince Hans as the charming rogue who almost succeeded in marrying Princess Anna in his attempt to gain control of the kingdom.