“It’s a fistful of Once Upon A Time,” said series co-creator Edward Kitsis about this Sunday’s two-hour block of back-to-back episodes.

In talking to Kitsis and co-creator Adam Horowitz earlier this week, we not only found out what’s surprised them the most about the current Dark Swan chapter, but also what’s coming for a number of the romantic pairings on the show.

Also: how will the core friendship of Emma and Regina be further tested as our Miss Swan gets pulled further and further to the dark side? And how will it affect Emma's relationship with Captain Hook?

And did the guys spill anything on what we’ll be seeing in the second half of Once Upon a Time Season 5 when the Dark Swan chapter ends?? Let’s see what they had to say about that and more...

TV Fanatic: With this chapter in particular, what has surprised you guys either in the writing of it or how it’s played out once the actors kind of got into it?

Adam Horowitz: I think it always is surprising with our actors who we believe are the best in the business now. They take what we write and bring something new to it and it’s just like with Dark Swan how Jennifer Morrison interpreted it and made it her own, and through all the characters, and I think that’s been a joy.

Edward Kitsis: I really think Jennifer brought her own thing to being the Dark One and that’s different than Dark Ones we’ve seen before and I think that’s been really great and it’s just fun to kind of see these characters brought to life. What I was most surprised by with the way Liam plays King Arthur is how he really lets you believe he’s doing what’s best for Camelot. There are times where I find myself going, ‘well maybe Arthur’s right.’

TVF: Since the first hour is called “Birth,” we can assume it something to do with Zelena but is there another kind of birth in the episode by chance?

EK: Absolutely. There is way more to it than that.

AH: The title “Birth” works on a different level than just the literal.

EK: And it will be very apparent to our fans at the end of the episode.

TVF: I know that Emma has to make a gut-wrenching choice in this episode. How much will it actually change her, this choice, and how will we maybe look at her differently?

EK: I think it will change her very much. Here’s the thing. I think it’s one of those episodes that a lot of the mysteries and the questions we’ve posed for the first seven [episodes], a lot of them are going to be answered in that first hour and so you’re going to look at, I think in a lot ways, the season in a new light.

TVF: How will whatever this choice is affect her relationship with Hook?

EK: Oh, significantly.

TVF: In terms of Emma’s journey being the Dark One, how will we see it affect her relationship with Regina moving forward? It’s already been affected quite a bit but is there even more coming?

EK: I think Regina and Emma have interestingly become friends and I think that it is an interesting friendship because they both share Henry and they were enemies when they started. So was Snow and Regina and they’re pretty close, too. I think Regina understands what the temptation to give in to darkness is and I think that Emma is going to come to rely upon her for help as the season progresses.

TVF: Tell me a little bit about Zelena’s journey with this. She’s so darn wicked but then you do get these moments where you might sympathize with her a little bit. Does that continue?

AH: I think that Zelena is wicked and she is an awful person who’s done awful things but she’s also human and this pregnancy, hopefully, is dimensionalizing her and making her look inward and face things about herself. But how she faces those things and what she does with that self-knowledge is always a wildcard with her.

TVF: Are we seeing any of Gold and Belle in these episodes, any progression with their storyline?

AH: Absolutely.

EK: We’re going to be slowly getting into the Gold and Belle of it all.

TVF: The second hour sounds like it’s focused on Merida. Are we seeing the other characters in the other hour?

EK: We’re going to see some of the other characters. We’re going to see Zelena. We’re going to see Arthur. We’re going to see Ruby. We’re going to see Mulan. But it is going to be very heavy in Merida.

TVF: Merida, Mulan and Ruby are teaming up so what’s the dynamic like and are there any surprises in how they work together?

EK: Merida has a backstory with Mulan that you’re going to see so and you’re going to realize that they predate what we’ve seen and I think the dynamic is very [much] what our show is, which is we rely upon our friends to help us through tough times.

TVF: Does this have anything to do with the LGBT story you guys talked about? I know you had said it would be in the second half but...

AH: As far as the LGBT story goes it’s one that we…I think the less said, the better in that we said that we’re planning to do it and our goal with is to not make it seem a unusual thing, but to do the opposite and make it just a part of our world the way it is in the real world and not marginalize anything and just make it seem as loving and beautiful as any relationship.

EK: But, yeah, that will be the second half of the season.

TVF: We’re seeing Merida’s backstory with her father and her father’s death. Will what we see shed new light on that death or their relationship?

EK:  Yes.

TVF: How much more are we seeing Mulan and Ruby throughout the rest of the season?

AH: There definitely are plans to see more of them, but it’s not in every episode but there are plans for them.

EK: As much as we would love for it to be every episode...

AH: It’s not regular but this isn’t a one shot thing either.

EK: We are kind of setting them up in the second half of the season. We are going to be seeing more of them and this will kind of explain where both of them have been.

TVF: For the second part of the season, are we seeing any seeds of what that story will be now or is it going to be a clean story from what’s happening now?

AH:  No, we’re definitely seeing seeds of it in the first half so they’re not going to be completely self-contained halves. I mean, there will be elements of the storytelling that are completely different in the second half and we’re wrapping up a lot of things from the first half but they’re connected in a more direct way than we’ve done in the past.

I’m sure you guys see the buzz on social media over the show because the fans are very passionate and vocal, which is what you want for any show.

EK: They get very passionate and so that it’s really fantastic to have such a dedicated fan base because it is so rare in today’s world anymore to get people so dedicated about things. For us, it’s really inspiring and it’s great. Like when we go to these events…we did New York Comic Con a few weeks ago and in the front row were three Emmas with the red jacket and the knit hat! Where else can you get people dressed as your character from the real world?  

Once Upon A Time Season 5 airs Sundays at 8/7c on ABC.

Jim Halterman is the West Coast Editor of TV Fanatic and the owner of JimHalterman.com. Follow him on Twitter.