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

“Once Upon a Time” producers teased the possible introduction of “Frozen” characters to the series back in March, and Sunday night’s Season 3 finale delivered. After the residents of Storybrooke all received their happy endings (all except for the formerly evil queen, Regina Mills, of course,) Princess Elsa found her way out of Rumplestiltskin’s dark magic vault and into the magical town in Maine, much to the surprise of viewers.

Following the epic two-hour event, “OUAT” co-creators Eddy Kitsis and Adam Horowitz dished on the series' upcoming Season 4 (set to premiere in the fall), sharing what viewers can expect from Elsa’s arrival and who might play the fan-favorite ice princess.

“We have an offer out to Adele Dazeem (Idina Menzel) to play Elsa,” Horowitz revealed to Entertainment Weekly Monday. Despite his casting admission, Kitsis remained coy about details regarding inviting the “Frozen” voice actress and “Wicked” Broadway star on to the ABC series, saying, “We haven’t thought about casting yet.”

While “OUAT” creators may be unsure about who will end up playing the ­42-year-old “Let It Go” star, they are in agreement about incorporating other characters from the hit Disney animated film (released in November 2013) on to the show. “We would be disappointed if Elsa was the only once we saw but we’re not quite ready yet to tell you who else we may encounter,” Horotwiz said, later teasing, “We do enjoy Olaf.”

No matter which “Frozen” characters make their small-screen debut, both Horowitz and Kitsis confirmed that the first half of Season 4 will take place in Storybrooke, not another realm. “I don’t want to say anything definitive, but we are not looking to in, like episode 3, go, ‘Oh my God, we’re not on Mars,’” joked Kitsis. “As always on the show, we like to show you different worlds. I would be let down if we don’t get to see Arendelle,” he added.

“OUAT” producers first teased the possible introduction of “Frozen” at the D23 fan event in March. Following the event, fellow “Frozen” voice actress, Kristen Bell (Princess Ana), shared her interest in guest-starring on the show. “That would be unbelievable,” Bell, 33, told E! News last month.