Guillermo del Toro is a workaholic. If he’s not directing a movie, he’s serving as executive producer. And if he’s not doing that then he’s off writing a script for a super expensive sequel. The man is a machine, and yet he still finds time to discover new talent. Case in point: siblings Andres and Barbara Muschietti, who adapted Mama from a short they originally created. Andres directed the film with del Toro’s blessing and guidance (while he was doing pre-production for Pacific Rim).

We recently got the chance to talk to del Toro and the Muschiettis about their new horror film. The acclaimed filmmaker discussed how he’s able to handle working on so many projects at once, and even shared a few details about upcoming projects (like Hellboy 3 and The Hulk). The Muschietti siblings talked about developing Mama (the monster) and taking the film from a mysterious short to a chilling, fleshed-out feature.

So we know that you were working on Mama at the same time that you were doing pre-production on Pacific Rim. How did you handle or plan that transition?

Guillermo del Toro: We planned it very strategically from the beginning. We gave a deadline to the studio where we told them, either we start production and pre-production on these dates, or we have to push the movie a whole year. That helped us into making the movie. I planned it so I could be with Andre and Barbara (Muschietti) through the pre-production, and through the first few weeks of shooting. I told the studio, if there’s a problem after those few weeks of shooting, we’re screwed. But if everything goes well, they’ll be coming out of it when I’m coming out of Pacific Rim.

Then we can be present on color correction, editing, sound mixing, whatever is needed. Fortunately for me, it worked great. We had a great director and a great producing partner. It was a seamless experience. I rented my stages for Pacific Rim to them. I rented some of the sets of Mama for Pacific Rim. And the offices where literally down the corner. I could walk 20-steps and I was in Mama (and vice versa). It was a seamless experience, but it could have gone wrong. There’s even a few props that I borrowed from Mama.

Which ones?

Guillermo del Toro: One is a tree. I said, we need a tree in a flashback, so I took the tree. And like three walls and a hallway. I just painted them another color.

In films like these the key is the children and believing them, and also being frightened by them. I’m always interested in hearing how directors talk to children, and being able to elicit those kind of performances. How much of that is casting? And how are you able to communicate with them to get what you need while onset?

Andrew Muschietti: Well casting is a big deal. One of the things that was in our minds from the very beginning was getting children who could do this in an incredible way. You know, getting those emotions to be credible. So basically it was finding the right actresses. It was not easy. We did a casting in Toronto and we didn’t find them, so we expanded the search.

Guillermo del Toro: To New York, Los Angeles, Great Britain.

Andrew Muschietti: So I finally found these two little girls that have completely different backgrounds and schools. Megan Charpentier has made films before so she mimics grownup actors. My approach to her was like an actor because I saw how she wanted to work. As for the younger one, Isabelle Nelisse, she was completely different. She hadn’t been in a movie before and she was completely instinctive and wild. Their backgrounds, though, are reflected in their characters. The older girl has memories of the real world, life in the city; and the other one is totally imprinted by the supernatural.

Barbara Muschietti: Little Isabelle, who plays Lilly, didn’t speak a word of English, and there was a lot of mimicking in the beginning. Until Andy’s French loosened up.

Andres Muschietti: The great thing is that I didn’t have to talk to her a lot because she was so sensitive.

Guillermo del Toro: By the end of month she spoke English. There are moments in the movie that I find a lot of truth in. I’ve directed kids in movies I’ve produced or directed and there’s two moments that, for me, stand out beautifully. One is the first encounter with Uncle Luke (Nikolaj Coster-Waldau) where Victoria doesn’t have the glasses, and then she puts them on and she says, “Dad.” I get chills every time I see it. And the second one is the moment where Annabel (Jessica Chastain) is struggling with Lilly and gets slapped by her. Anna warms her hands. It’s a moment out of a Helen Keller biography. It’s really intense and beautiful. It’s a moment of pure truth between the characters. People think that you come in to produce, to teach, but you also come in to learn. In this movie, those two scenes alone were great to see achieved.

How was Jessica Chastain’s relationship with the young girls on set? And can you also talk about casting her as well?

Guillermo Del Toro: She was very protective of them in a good way. She was always talking about them as actors. And she had a great partner.

Barbara Muschietti: She asked us not to leave her alone with them because she would fall in love with them, and that would be hard because of the characters they play.

Guillermo del Toro: But it was impossible to keep them away from her. They bonded. She was very aware of their school time. She was like a union worker. And Jessica is a machine. She can go 25 takes and do better and better. But, casting her. When we started she was not yet a known commodity to the studio. And on the other hand, to her agents and managers, a thriller was not the safest bet for her as an actor. Fortunately Pan’s and Orphanage, these movies were helping this movie. It was obvious that we had a movie that we wanted to make for the right reasons. It’s not a dumb movie. As soon as we met her, she said she wanted to do it. Her and Andy bonded over ukuleles. And we all bonded over karaoke. We’re all karaoke freaks.

This film started off as a short. What was it like building a feature-length film out of that?

Barbara Muschietti: It was reverse process. Logically you would have a story and pick out a little piece of that story and make a short, but we just made that short. We were left with a lot of questions. That’s what inspired us was Guillermo telling us to make a movie out of it. That was the process.

Andres Muschietti: We had to find a context to build around it, and answer the questions that the short film raises but in a mysterious way. We had to translate that mystery into full-feature. You can get away with not answering all of those questions in a short. But we had to answer them in the feature, as the mystery unfolded and still make a compelling mystery.

Guillermo del Toro: We went all the way to complicating it and all the way back. We developed very strange stories for the characters. But what’s great about Andy is that nothing phases him. I can argue with him for half-an-hour on the merits of something and if he doesn’t like it, he’ll tell me. That is true with Barbara. The have a Yin and Yang relationship, I’m not even sure they’re brother and sister. The same with Neil Cross. We’re four completely different energies, sometimes harmonious, other times, not so much. And we made a movie that I’m really proud of.

How did you convince the studio to go along with the ending?

Guillermo del Toro: For that ending, I made sure I had final cut. We financed the movie in a way that we had autonomy in the decisions that we could preserve the ending. And after all of those preparations, we sent it to the studio, and the studio went, ‘We love it!’ We were shocked. In my experience, that normally doesn’t happen. We had a tone shift that I’ve done before, in Pan’s Labyrinth, we did it on The Orphanage, where we start as a horror story and end up on a very moving note. It’s very sublime at the end. I was also prepared for that being something the studio was up against. But they supported it it. I wish I could tell you, I went in a room and slammed my hand and punched the wall, but it was really super easy.

Do you think that’s just because of the current climate? We just watched Hunger Games earlier this year, and there were kids mass-slaughtering each other. They kept it very classy, but it was shocking to see them kill a 5-year-old.

Guillermo del Toro: No. I think that what happens is, well, one of our tasks all together was to watch the performance of the kids so that ending would play. When we saw one of the early cuts, we realized the ending felt organic.

Wasn’t the film originally suppose to be released in October? What happened?

Barbara Muschietti: It was never coming out in October. Never.

Guillermo del Toro: We dated the movie once, and it was January. We looked at all the weekends and there were no more great weekends left in 2012.

Can you talk about designing Mama herself? What was the process of how she came about?

Andres Muschietti: Well I draw everything.

Guillermo del Toro: He’s a great artist by the way.

Andres Muschietti: Yes, I draw with my feet.

Guillermo del Toro: Like Daniel Day Lewis in My Left Foot. [Laughs]

Andres Muschietti: The character is so ambitious. All the stuff I did was on the verge of being funny and you have to be very careful with that. When I was little there was a print that scared the crap out of me. It had someone with a stretched neck and empty eyes. I was always terrified by that. Usually monsters and creepy characters tend to go to common places, and I thought that I was doing something different.

Mama also seems to be tied to nature with the insects, and when she comes out of the wooden walls. Was the nature-theme intentional?

Andres Muschietti: Very much.

Can you also talk about sound design? Sometimes it sounds like a tree bowing.

Andres Muschietti: When it comes to sound, you never go to get what it is. For us it was about finding unusual sounds. We didn’t put water sounds to Mama. It was more about creaking. It’s mainly a baby. Her voice is baby sounds backwards and pitched down.

Guillermo del Toro: We wanted a physical effect, not a digital effect. We went for that, and Andy designed a system of cables to be attached to the actor so that when the actor moved, there were people moving the arms and the legs in different directions. So the spastic movement feels unique. The movement of the body is jerky, and very gentle movement in the hair. So the harmony, or lack of harmony, of those two things speak a lot about personality. And Andy didn’t want her to be translucent but he wanted her to sink in the floor, or sink in the walls. I think the result is realistic. It feels palpable.

You have loads of projects coming up. Have you written the script for Hellboy 3?

Guillermo del Toro: No. Up until a few months ago there were three or four parts to the equation that we couldn’t agree on doing. We finally agreed, but haven’t found anyone who wants to finance it because it’s so expensive. And it’s not the happiest ending, so… it’s not an easy task. The other thing I can say is we do it right or we don’t do it. Either we leave those beautiful juicy answers unanswered or we answer them properly. Listen, I’m a workaholic. I do have five or six projects active. And every time I share anything about them I curse myself, but I can say that I wake up so early and I go to sleep so late. I just compartmentalize. Two hours for this, six hours for that. I get to the Pacific Rim editing room at 9, leave at 5. Anything before or after, I try to dedicate to the other projects that are active.

Can you say a few words about The Hulk?

Guillermo del Toro: Since The Avengers came out there’s been radio silence. I can speculate one way or another. I met once with Marvel. We talked again about it. We delivered two drafts of the screenplay, but they said they’re waiting for a writer. That’s the official word, to do a re-write. I haven’t heard. I know as much as you do now.

Mama hits theaters January 18, 2013.