Once Upon A Time "Once Upon A Time" actors Jennifer Morrison and Robert Carlyle at the ABC Summer TCA Press Tour in Beverly Hills , California in 2011. Photo: Reuters

“Once Upon a Time” fans were shocked by the incorporation of Disney’s film “Frozen” into the hit ABC series during its Season 3 finale on Sunday night, and they weren't the only ones. In an interview with Time magazine, “OUAT” show runners, Adam Horowitz and Eddy Kitsis, said the cast was kept in the dark about the Princess Elsa arrival sequence.

Horowitz said only a “handful” of “OUAT” cast and crew were privy to the shocking finale closer, with a majority kept in the dark by a script containing an alternate, unaired ending. “Many people who work on the show didn’t even find out until afterwards,” he said.

While the stand-in conclusion didn’t make it to airwaves, Horowitz remained mum when asked to disclose details about the unused Season 3 closer. "It’s something we’re probably going to want to use [later],” he said.

The two men later hinted that the storyline will, as usual, play into its Disney-esque storybook theme. “It’s another iconic Disney totem,” Kitsis said, adding, “We’ll leave it at that.”

News of a secret alternate closer comes on the heels of Horowitz sharing another unaired scene with viewers. On Twitter Monday, he disclosed the script for a scene between Emma Swan (Jennifer Morrison) and The Evil Queen/Regina Mills (Lana Parilla).

“Here it is. Thank you all! Without you all there would be no #OnceUponATime -- hope to see ya in the fall for season 4!” Horowitz tweeted next to an image of the script's sequence, which was reportedly planned to occur after Emma’s "Neal flashback" and before her time spent in the queen’s slammer with Robin Hood’s wife.

Once Upon a Time ABC introduced "Frozen" film character Princess Elsa to "Once Upon a Time" Sunday night. Photo: ABC/Once Upon a Time

Horowitz told Entertainment Weekly on Monday that “Frozen” voice actress, Idina Menzel, had been invited to star as Elsa on Season 4 of the live-action ABC series.

“OUAT” producers first teased “Frozen” in March at a D23 fan event. “Frozen” voice star Actress Kristen Bell has shared her interest in guest starring on the show. “That would be unbelievable,” Bell told E! News last month.