11 Things to Know About ‘Once Upon a Time’’s 100th Episode and Beyond

Over the course of 99 episodes, Once Upon a Time has flown to Neverland, stormed into Oz, quested in Camelot and gotten frozen in Arendelle. But for the series’ milestone 100^th outing (and also the midseason premiere), creators Edward Kitsis and Adam Horowitz are heading to the most intimidating realm yet: the Underworld. We caught up with the executive producers to find out what magic they’ve got up their sleeves for the monumental occasion—and whatever morsels they’d give us about the rest of the season.

Surprising objectives will soon be revealed.
When we last saw our heroes, Emma Swan (Jennifer Morrison) was leading them all to the Underworld in the hopes of bringing back her recently deceased lover, Captain Hook (Colin O’Donoghue). But “the journey down to save Hook is just the launching point,” says Horowitz. “By the end of the episode, the audience will realize that there are stakes that are even larger, and it’s going to be a test for all of our heroes and villains in a hopefully unexpected way.”

Emma Swan and Co.

The Underworld won’t be hell…
Instead, think purgatory. “In the Underworld, we find folks who have unfinished business,” says Horowitz. Kitsis describes it physically as “a more hell-ish version of Storybrooke,” the reason for which will be explained in the back half of the season.

…And you don’t have to be a bad person to be there.
“A hero’s job is to help them move on,” says Kitsis. “Because of that,” adds Horowitz, “it’s not simply populated by villains or bad people. Anyone can have unfinished business.”

Familiar faces will come back from the dead.
Thanks to the setting, several dead characters return for the episode, including Regina’s mother Cora (Barbara Hershey) and Rumple’s father Peter Pan (Robbie Kay). The Magic Mirror (Giancarlo Esposito), Regina’s father the Valet (Tony Perez) and the Blind Witch (Emma Caulfield) also appear, and Cruella De Vil (Victoria Smufit) shows up later in the season, though Kitsis says “her presence will be felt” in the premiere. He also teases that there could be more surprise returns not yet announced.

“The Boss” (as in Bruce Springsteen and Horowitz) will get a shout-out.
The 100^th episode is entitled “Souls of the Departed,” which of course refers to the characters our heroes will reencounter in the Underworld. But it’s also an intentional nod to the 1992 Bruce Springsteen song that Horowitz loves.

Cora’s back.

Regina’s going to have mama drama… or will she?
When Cora died in Season 2, her last words to Regina (Lana Parilla) were, “You would’ve been enough,” which means a reunion could be a happy one. “We were very interested in what happens next. After that incredible realization, what would it be like between the two of them?” says Horowitz. “We’re really excited for how that relationship can progress in a way that neither of them ever expected that it would get a chance to.” Cora’s arc will also continue beyond just the 100^th episode.

RELATED: Why Once Upon a Time Has a ‘Long, Bright Future’ Ahead

Don’t worry, Belle won’t be left in the dark too long.
As we know from the midseason finale, Belle (Emile de Ravin) isn’t headed to the Underworld. But “she’s going to get dragged into the story,” says Kitsis. “That’s very much on our mind, following up on a pretty major development with Gold,” says Horowitz. “Belle is a bit in the dark, so how that [works out] is pretty important to us.”

Fresh blood from Disney’s Hercules will liven things up.
Characters from the 1997 Disney flick Hercules will be introduced, beginning in the premiere with Hades, played by Ally McBeal’s Greg Germann. “He was able to take this character and play the menace, play the humor, but also find a real sadness and pain at his core, which is driving him,” says Horowitz. As for Hercules and his other half Meg, they’ll show up in the second episode back.

Of course, Hercules and Hades will have connections to Storybrooke residents.
Per usual, the Once world will be interpreting the movie characters in its own way. Says Kitsis, “For Hercules, the first spin on it is that he has a relationship with one of our main cast from their past.” Hades also knows one of the main characters, as well.

Ruby (left) and Mulan

Plus, more characters from the first half of the season will be back.
“What we tried to do this year was not keep the two halves of the season completely separate,” says Kitsis. “They are their own arcs in many ways, but the ripple effect of the first half of the season is felt later in the second half.” Ruby (Meghan Ory) and Mulan (Jamie Chung) will appear towards the middle of this half, and Merida (Amy Manson) and the Camelot folks will also reappear.

And, the long-awaited LGBT plotline is coming.
Kitsis admits that he wished they’d never revealed the story thread was coming. “A large part of our fanbase has been asking [about it] and living with it for eight months,” he says. “So now they have it in their heads one way…and it’s going to be very hard to meet [expectations].” Still, the producers think they’ve done it justice. “Our hope is that it doesn’t come off as a ‘very special episode,’ ” says Kitsis. “Our hope is that it’s just a part of the fabric of the show, that the audience will enjoy it and that it doesn’t feel marginalized in any way. It just is.”

Once Upon a Time, Midseason premiere, Sunday, March 6, 8/7c, ABC