The Queens of Darkness, which consists of Maleficent, Ursula, and Cruella de Vil, are then reformed by Mr. Gold with plans to rewrite the Once Upon a Time book with the help of the Author, resulting in the creation of an alternate reality known as Heroes & Villains.

[42] During San Diego Comic-Con 2014, it was officially announced that Ginnifer Goodwin would be returning as Snow White / Mary Margaret Blanchard along with fellow cast members Jennifer Morrison as Emma Swan, Josh Dallas as Prince Charming / David Nolan, Colin O'Donoghue as Captain Killian "Hook" Jones and Jared S. Gilmore as Henry Mills, Lana Parrilla as the Evil Queen / Regina Mills and Emilie de Ravin as Belle.

On July 1, 2014, it was announced that Scott Michael Foster and Elizabeth Lail had been cast as Frozen characters Kristoff and Anna, respectively.

[47] On July 28, 2014, Tyler Jacob Moore and John Rhys-Davies were both announced to be playing Prince Hans and Grand Pabbie, respectively.

The third episode, "Rocky Road", revealed that the roles of two of Hans' brothers, Franz and Jurgen, had been given to Nils Hognestad[50] and Marcus Rosner[50] respectively.

[51] Returning recurring cast members include Sean Maguire as Robin Hood,[52] Christie Laing as Maid Marian,[52] Giancarlo Esposito as the Magic Mirror / Sidney Glass,[53] Beverley Elliott as Granny,[54] Lee Arenberg as Dreamy / Grumpy / Leroy,[55] Raphael Sbarge as Jiminy Cricket / Dr. Archie Hopper[56] and Keegan Connor Tracy as the Blue Fairy / Mother Superior.

[61][62] It was announced on November 5, 2014 that Victoria Smurfit would be portraying Cruella de Vil in a recurring capacity later on in the season and that hints will be placed in the next few episodes.

[74] The fifth episode, "Breaking Glass", saw the return of Abby Ross as a teenage Emma,[60] who later also appeared in "Shattered Sight",[76] "Best Laid Plans"[75] and "Lily".

The sixth episode, "Family Business" saw the return of Eric Keenleyside as Maurice, Belle's father,[71] and introduced Darcey Johnson as Oaken.

[51] Patrick Fischler was cast in the recurring role of a Peddler[77][78] initially named Gorin,[79] who first appeared in "Best Laid Plans"[75] where he was revealed to also be the Author.

[88][89] Agnes Bruckner was confirmed to appear in a three-episode arc in the role of an adult Lily,[90][91][92] a friend of Emma from her childhood who was portrayed by Nicole Muñoz in the fifth episode, "Breaking Glass".

[95] The episode that aired on March 22, 2015, "Poor Unfortunate Soul", saw the return of Christopher Gauthier as William Smee[96] and introduced Tiffany Boone as a younger version of Ursula.

[102] The website's consensus reads, "The addition of a Frozen subplot feels like a marketing angle, but Once Upon a Time's season four shines, adding more layers to an already complex story.