Following a 19-minute Once Upon a Time in Wonderland preview, which features John Lithgow as the voice of the White Rabbit and establishes that the show takes place concurrent with the main Once series, D23's Jeffrey Epstein introduced executive producers Adam Horowitz and Edward Kitsis for an entertaining presentation at the D23 Expo on Saturday that offered rabid fans -- known as "Oncers" -- enlightening details on Once's upcoming third season and Wonderland's debut year.

As seen in the preview, the show will center on Alice, the White Rabbit and the Knave of Hearts as they attempt to find Alice's long lost love, the former genie known as Cyrus. Beyond that premise, the producers confirmed that the series will use the same "flashback" structure as the main show. Kitsis added that Lost alum Naveen Andrews will feature as Jafar, whose story will play out along with Alice, her lost love Cyrus, the White Rabbit and the Red Queen.

"We'll find out about the Knave of Hearts and why he's quite knavish. It will be a completely story," Kitsis explained. "You won't have to wait five years to see how [we resolve it]."

Unlike Once Upon a Time's multi-year, on-going conflicts between Emma and Regina, Rumpelstiltskin's designs for Henry and the perilous fate of the people in Storybrooke, Wonderland will wrap up its search for Cyrus by the season's end. Subsequent years will continue to feature Alice and her crew as they venture across the many realms of fantasy and myth. "Should this work, if you like [it], we would be thrilled to come back with more stories with this cast," said Horowitz.

Asked if the audience will see certain homages to the classic Disney animated film, Kitsis teased that "you will see a certain blue dress."

Horowitz added that the Cheshire Cat will appear in the pilot, but other characters from stories and poems of original Alice creator Lewis Carroll, which he characterized as "deep cuts," will make their way into the show as Alice searches for Cyrus.

As with Emma on Once, Cyrus is a completely new creation. Epstein wondered what led to his creation. "Alice is a character who was curious enough to follow a rabbit into a hole," Kitsis said. From that starting point, they knew her love interest would have to be someone who complimented that curiosity and settled on a genie.  "We love that she would naturally fall in love with a genie," he continued. "A genie has lived many lives, but a genie has also watched people ruin their lives." As the audience will discover over the course of the season, Alice and Cyrus are "kindred spirits."

In both the 19-minute preview and the shorter version available online, Alice starts the series in a Victorian era sanitarium, but the long preview makes it quite clear that the Knave lived in post-curse Storybrooke. Clearing up any possible confusion, Kitsis explained how the three major realms in Wonderland exist relative to one another. "There's our world, where Storybrooke is, then there's a realm of stories where you find [late 19th Century characters]. Alice is in that Victorian England; [it] exists concurrently [with us]."

Horowitz added that though they have plenty of rules for their universe and a map of how the realms work, the audience won't "need a flow chart" to watch the show.

Since Wonderland takes place in the realm previously ruled by Once villain Cora the Queen of Hearts, Kitsis teased that she may appear on the show, at least in a flashback. "In the pilot, you see the Red Queen, but you don't see the Queen of Hearts," he began. "Although, she had to learn all her tricks from someone."

With a smile, Horowitz added, "I would be disappointed if she didn't [appear]."

Turning away from Wonderland, Epstein moved the discussion toward Neverland as Emma, Snow, Charming, Rumpelstiltskin, Regina and Hook set sail for that realm in search of Henry at the end of "Once Upon a Time's" second season. Noting that the theme of the second season was "magic is coming," he asked the producers if the early part of season three would have its own theme.

"We're excited to be back?" quipped Horowitz.

Offering a more serious answer, Kitsis summed up the theme in one word: belief.

Neverland, as a reality, is powered by the belief its inhabitants pour into it. By traveling there, the major Once characters will discover how much power their own beliefs about themselves contain and must come to grips with those beliefs in order to become their best selves. "It's important that they all become who they are. And they all need to work together to save Henry," explained Kitsis.

"If the key to season one is that they don't know who they are and in season two, it was wrestling with themselves," added Horowitz. "Then in season three, it's about confronting who they really are."

Horowitz also teased that this Neverland is "a little different from what you've seen before."

With that, the producers shared a clip from the premiere episode in which Rumpelstiltskin, back in Enchanted Forest attire, receives a message from one of Peter Pan's Lost Boys. Pan is willing to let the Dark One stay in Neverland for as long he likes provided he does not attempt to retrieve Henry. Rumpelstiltskin refuses the terms and the Lost Boy, whom the producers revealed is named Felix, tosses a doll at him. Recognizing the simple cloth-and-twine toy, the Dark One is brought to tears.

"Pan doesn't seem like he's going to be nice," Epstein said.

"There seems to be a lot of fear around Peter Pan," Horowitz offered. The producer also noted that Rumpelstiltskin's apprehension around Pan should give some indication of how formidable the character will be during the season.

"We were looking for a twist on Pan and [to explore] what happens when a person chooses to live in a place where you don't grow up," Kitsis clarified.

Horowitz added, "When we meet Peter Pan, he has a very clear objective and a reason that he doesn't think is evil."

Asked if the trip to Neverland will help Snow out of the dark place she entered toward the end of season two, Horowitz recalled Snow's speech in which she said killing Cora was the "easy way." To him, that statement was "the rebirth of the light" in Snow.

"In Neverland, she has to return the hope to everyone," Kitsis continued. Part of returning that hope will be creating a parental bond with Emma, who now believes that Snow and Charming are her parents, but does not look at them as her parents.

Meanwhile, Storybrooke will be touched on in the first eleven episodes of the season, but, as Horowitz explained, the focus will be on the main six "Fairy Tale Avengers" and their mission in Neverland. That said, the producer teased the bond between Belle in Storybrooke and Rumpelstiltskin in Neverland will be touched upon and tested during the first half of the season.

Aiding the momentum of the story will be its broadcast schedule. When Once returns on Sept. 29, it will air on ABC for 10 weeks, taking the winter off and returning in the spring with another 11 episodes that will form its own second story arc for the season.

Though set firmly in Neverland for the first half of the run, the producers teased Neil's adventure in the Enchanted Forest will be seen -- in fact, Aurora and Mulan make an appearance in the season three premiere -- and one subplot will feature a growing tension between Emma and Hook.

"They use the same eyeliner," joked Kitsis. "He's going to be extra-handsome [and] Charming doesn't like the effect he has on his daughter." More of Hook's past will also be revealed in the first five episodes as a flashback plot will revolve around how he became a pirate.

And though the focus will be on the existing characters, Wonderland will see the premiere of a few well-known Disney characters, including Tinker Bell and Ariel.

"There's a good chance at seeing Ursula," teased Kitsis. "And a good chance of seeing a guy named Eric."

More information about "the home office" will also be revealed, but the producers gave no further details on that front.

"You're going to learn about Tinker Bell's connection to another character," added Kitsis. "Ariel will also have a connection [to this character]."

Robin Hood "may" also play a more prominent role as the season progresses and Horowitz offered one final tease: "We may meet someone who might be a great soulmate for Regina, if she can let love in."

While it is fun to bring in more characters from the Disney stable, Kitsis mentioned that it requires a good story for a character like Ariel to make her way onto the show. The producers considered introducing her since the pilot, but never found a natural, story-driven way until the mermaids of Neverland provided an appropriate environment for her to appear.

"For us, it's an honor to write Snow White and the dwarves and these great characters. We feel like to kids that ran into the living room of Disney and took toys off the shelf," Kitsis explained. Continuing the metaphor, he said it was important to only add a toy when it makes the most sense.

At the same time, the producer also hopes to find a story that allows them to introduce Rapunzel. Horowitz said he would love to see Tiana from The Princess and the Frog make the trolley-ride to Storybrooke.

During the audience Q&A, the producers were asked if Once and Wonderland will see much character crossover. According to Kitsis, it is unlikely that Emma and Snow will ever be seen, but Cinderella and Grumpy are scheduled to appear. "Wonderland is kind of its own vibe," he added. Though substantial crossover will be rare, character appearances will not be unheard of.

Horowitz interjected, "We're sprinkling breadcrumbs throughout."

Both producers told a fan they would like to eventually find the characters cross over the rainbow into Oz. "There are many realms that are on the docket should we get there. You'll see some clues to places we're thinking about," said Horowitz.

Considering all the jumping between realms in the two shows, the producers were asked if actor Sebastian Stan and his take on the Mad Hatter will ever be seen again. "Jefferson is now the Winter Soldier," Horowitz replied.

Kitsis added that it comes down to scheduling. Stan is an in-demand actor that Once now must share with the world. "We have no plans to recast the Mad Hatter," Kitsis clarified. "But we have been greedy with him and now other people have taken him."

Similarly, actor Giancarlo Esposito will make a cameo appearance this season back behind the Magic Mirror in an episode that reveals Regina's reaction to true love's kiss reviving Snow White back in the Enchanted Forest. Though Esposito is a series regular on NBC's Revolution, the two productions were able to come to an agreement with the actor returning to Once for a single day of shooting.

Horowitz joked, "The problem with these great actors is that other people want them."

Since Aurora will be seen in season three, a fan wondered if her past with Maleficent will be explored or if the character will ever be seen again. Horowitz offered an enigmatic answer: "We've not forgotten about her."

Finally, the producers were asked why Greg and Tamara, the magic-stomping humans running afoul of Storybrooke, have such "dark hearts." The producers gave an answer that highlights one of the most interesting thematic conflicts in the show.

"We hate Greg and Tamara because they're so cynical," Kitsis explained. "They stand for everything we hate. What makes their hearts dark is that they don't believe."

"The magic we want in the world is something that they're afraid of and that fear turns into hate," Horowitz added.

Wrapping up, the producers thanked the audience for keeping Once alive and allowing them the opportunity to create a spinoff. "We thought we'd be cancelled [the first year]," Kitsis said, adding that when they write the show, they strive to create what the fans want to see.

Once Upon a Time returns Sept. 29. Once Upon a Time in Wonderland premieres Oct. 10.