Season 4 of Once Upon a Time is well underway, and fans of the fairy tale inspired series are looking forward to the Frozen characters appearing on the show.

At the end of Season 3, Elsa was seen from behind, and fans were surprised by her arrival in the finale. Her story wasn't touched on, but the show's creators did confirm that she was being held in Rumpelstitskin's vault. Anna and Kristoff were later confirmed to be joining the characters the Once Upon a Time cast.

Georgina Haig, of Fringe and Reckless, will be playing Elsa, while Elizabeth Lail was cast as Anna. Kristoff will be played by Scott Michael Foster.

The show's co-creators, Eddy Kitsis and Adam Horowitz, revealed that the characters are very much based on the original movie, but with some added quirks and storylines typical of the "OUAT" universe.

"For us, I think this is Elsa from Frozen. That was kind of the inspiration. Will there be our own elements to it? Yes. Like all things we do with Snow White or Peter Pan or Captain Hook, we take our own kind of twist to it but remaining faithful to the actual essence of the character," they told Entertainment Weekly.

Horowitz was also quick to add that they are not going to redo the movie, because they feel it would not be in anyone's interest.

"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 in the universe of (what) everyone fell in love with this past year," Horowitz added.

Season 4 of Once Upon a Time will premiere in September 2014.