A lot of Disney fans are probably excited that the beloved "Frozen" characters, especially the sisters of Arendelle, will head to Storybrooke.

The fourth season of "Once Upon A Time" will unravel the mystery of how Elsa was trapped in an urn in Rumplestiltskin's castle, according to showrunner Adam Horowitz. He said that one of the mysteries next season would be about Elsa's incarceration in the fortress and how she ends up in Storybrooke. Horowitz also told TV Fanatic that the storyline in the TV series take place after the events in the "Frozen" movie.

Meanwhile, Queen Elsa will clash with the other queen residing in town, Regina. Regina will feel threatened by the arrival of the Snow Queen, but the evil queen will defend her throne. Based on the extended trailer for the upcoming season of "Once Upon A Time," fans will see Elsa (Georgina Haig) declaring that she is the queen, which annoys Regina (Lana Parrilla).

Now, the evil queen is back to her former wicked ways after being heartbroken. She enlists the help of her old pal, the Mirror, to help her scare away the ice queen. "She needs to be removed," Regina proclaims. It is still unknown what she will pull out her bag of tricks to eliminate Elsa. However, fans can bet on some magical action between the two.

Elsa and Regina have a lot of things in common, such as their background of love and losing it as well as their desire for power. Thus, the audience can expect a battle for supremacy next season as Elsa is reported to be a villain.

The fourth season of "Once Upon A Time" will come back on air on Sept. 28 on ABC. The show creators and executive producers Edward Kitsis and Adam Horowitz confirmed that Elsa, Anna and Kristoff will definitely appear in show next season.