"Once Upon a Time," the ABC fantasy-drama that revisits and reconstructs everyone's favorite fairy-tales, has just entered season 4, and it's introduced audiences to new characters, Elsa (Georgina Haig), Kristoff (Scott Michael Foster) and Anna (Elizabeth Lail), from 2013's instant classic "Frozen."

Episode 1, "A Tale of Two Sisters" premiered on Sunday, Sept. 28, and fans witnessed the much-adored series fold the plot of the popular Disney film into its storyline. The series' producers have gained praise for "doing the film justice." Also, actors were able to "seamlessly bring iconic characters to life."   

During the first episode, Elsa (queen of Arendelle with the power to control snow and ice) is released from an urn that belongs to Rumplestiltskin's (Robert Carlyle), and she begins to wander the streets of Storybrooke. She is quickly pursued by Emma (Jennifer Morrison) and Hook (Colin O'Donoghue), who've taken to investigating the mysterious, icy threat that's trailing through the streets. At the same time, Gold (Robert Carlyle) and Belle (Emilie de Ravin) begin an in-town honeymoon within a picturesque mansion; Elsa looks to uncover what really happened to her parents; and Regina (Lana Parrilla) summons the magic mirror to help her find the author of the "Once Upon a Time" book so she can finally have the happy ending that she believes she rightly deserves.

Prince Hans (Tyler Jacob Moore) from the film "Frozen" will also make an appearance on "Once Upon a Time" in episode 3, titled "Rocky Road."

The fourth season will have numerous cool developments. Will Scarlet aka Knave of Hearts (Michael Socha) will become a regular. The Snow Queen (Elizabeth Mitchell) will become the season's main antagonist. Also, during the second half of the season, Maleficent (Kristin Bauer van Straten) will return to the series for a major arc, posing as the main villain.