Executive producers Eddy Kitsis and Adam Horowitz talk to THR about the decision to bring the icy "villainess" to Storybrooke, as well as obstacles facing Regina/Robin Hood, Hook/Emma and Belle/Rumple in season four.

[WARNING: Spoilers ahead from Sunday's finale of Once Upon a Time]

Once Upon a Time is bringing an icy new character for season four and the timing couldn't be more appropriate.

The final seconds of Sunday's season-three finale of ABC's fairy-tale drama revealed the Storybrooke arrival of Elsa, from Disney's Oscar winner Frozen. The process of bringing the character to Once Upon a Time evolved naturally, executive producers Eddy Kitsis and Adam Horowitz claim. After the co-creators watched Frozen several times, they came up with an idea they felt adamant about doing.

STORY: 'Once Upon a Time' Finale Teases Icy Fairy-Tale Character for Season 4

Following Sunday's big Frozen reveal, Kitsis and Horowitz talk to The Hollywood Reporter about how it came to pass, whether they have their eye on an actress and the unexpected arrival of Regina and Robin Hood's temporary bliss.

Was that the Snow Queen, or Frozen’s Elsa, in the final moments?

Adam Horowitz: That was Elsa.

So you’ll base the character on Frozen and not the original fairy tale?

Horowitz: We are dealing with the world of Frozen. We are honored to be allowed to do it. We loved the movie. We fell in love with it when it came out last year like everyone did, and we want to do our best to do it justice.

Eddy Kitsis: [What] we loved so much about the character of Elsa was that she was considered a villain but she never really was. She was misunderstood. That, on our show, speaks to us so strongly, that it was a toy we had to play with. It’s funny because I see lots of people [saying] “Oh! Did Disney ask them to do this?” It’s quite the opposite. It’s actually quite hard to get these characters on the show. It’s not like you get a call from Mickey Mouse saying, “I want you to sell mermaids this week.” It’s the opposite. It’s very hard to get these. We were very honored that Disney allowed us to take this toy off the shelf and let us play with it.

How did you come to the decision, then, to introduce Elsa? You have to admit it’s quite timely.

Horowitz: After the movie came out last November, and seeing it three more times, we loved it. And our brains start to get activated. It’s like anything on the show. Once our brains are activated and an idea starts to take root, we want to do it. And we started playing with the idea and it grew in our heads about what it could be, we went to the studio and network and pitched it to them. And they said, “OK, here you go.” It was really as simple as that.

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Kitsis: We talked to Disney also.

Horowitz: It’s like any idea we try to do on the show comes down to “Wow, wouldn’t it be cool …”

Will Disney have substantial input in how she’s incorporated into the show or will you have free rein?

Horowitz: The process I’m guessing it will be similar to how it’s been with all these characters. In many ways, it’s like using Snow White, using a character from Frozen -- it’s just a hundred-year difference. Our scripts and our ideas get vetted by the studio and the network and Disney’s brand management people, and I’m sure that process will continue.

Do you have someone in mind to play her or are you currently casting?

Horowitz: Honestly, we literally delivered the finale on Friday. We’ve got two weeks right now to decompress a little bit.

Kitsis: To not think. We’re trying our hardest to not think for two weeks, but when the two weeks is done and Memorial Day is done, then our first order of business will be who is Elsa.

Horowitz: There will be some announcements, but right now we’re decompressing.

When should we first expect to see her in season four?

Horowitz: I would expect it to be very, very early.

Kitsis: I would hope that it’s in the premiere.

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Let’s get into the other big reveals from the finale too, if you don’t mind. First of all, poor Regina. With Robin Hood’s dead wife resurfacing in Storybrooke, where does this put Regina and Robin Hood’s relationship?

Horowitz: It’s going to be a challenge because we saw feelings start to grow between the two of them, obviously. It’s a conundrum because Robin Hood believes his wife is dead and he clearly had feelings for her, so that’s going to be hard for him. It’s going to be hard for Regina. It’s a funny thing. With Regina, this is a character who's very different from the character we met in the pilot. She’s grown and changed, so how she reacts to adversity now is going to be very different from three years ago. That’s one of the exciting things for us to explore, which is how does this new evolved Regina handle this situation.

Are Regina and Emma back to being nemeses, for lack of a better term, in season four?

Horowitz: We're not going back, we're going forward. If they were going back, what would've happened is she wouldn't have incinerated her on the spot.

Kitsis: Or tried to rip her heart out. For us, what's interesting is it takes Emma 66 episodes to call her mom and dad "Mom and Dad." It took her that long to open her heart and the same with Regina. How do the characters relate to this now as opposed to when the show started three years ago?

Another big moment was Hook and Emma coupling up. What's in store for them?

Kitsis: We know Emma's a tough one, and I think we want to explore exactly that: What does it mean? What does it mean now? Is it a kiss or is it more? If it is more, how does Emma feel about starting a relationship after just destroying one?

We also have to talk about Present-Day Hook punching Past himself in the Enchanted Forest in the Past. Did you want a clone scene?

Kitsis: We loved the idea of Hook being jealous of himself. We wanted Hook to punch himself.

Horowitz: And kissing Emma. It was a fun moment for us, but there was a serious subtext to it, which is that it's Hook looking back on the man he was. He's another character who's evolved some. He knows that that Hook with Emma is not something he wants to see.

What's the likelihood Belle and Rumplestiltskin's marriage will hit a rough patch?

Kitsis: Unfortunately for Belle, she doesn't realize Rumple has started off their marriage lying to her. But Rumple's feelings for her are genuine. Last year, we saw a Rumple who sacrificed his life to save everybody and then was brought back from death. Because he was held by the Wicked Witch, we never got inside his head to see how he was feeling. We're hoping to explain why he hid the knife, why he's lying to Belle and what he's up to; that's all season-four business.

Were there other names besides Neal that you were toying with for Snow and Charming's baby?

Kitsis: It was between Neal and Scott.

Why Scott?

Kitsis: No I'm kidding. (Laughs.) When we sat down to talk about the name, it was kind of like that. It has to be Neal or else it will be something like … John, which doesn't mean anything. It was funny because it was hanging over us. We were thinking, "What is it? What is it?" And then it was obvious: "Oh, it's Neal!"

There were some thinking it could have been Baelfire.

Kitsis: Yeah, I know. Prince Baelfire sounds better than Prince Neal, but in Storybrooke, Neal is easier. But maybe it's a different name -- he gets to be Bae in the Enchanted Forest if he ever finds it there.

We saw a lot of familiar faces in the finale, such as Ruby. Should we expect characters like her who had larger roles in early seasons to be significantly featured in season four?

Kitsis: We love Meghan [Ory] and we love that character and we hope to see more of her next season. We would've seen more of her this season but she was on another network on another show [CBS' canceled Intelligence].

Horowitz: We're at the stage where we're trying to figure out all that stuff. We love Meghan and she's [been] a huge part of the show since the pilot.

Email: Philiana.Ng@THR.com

Twitter: @insidethetube