Spike Jonze and Dave Eggers relive the cold winter's day when they went to visit famously prickly writer Maurice Sendak, to talk about filming Where the Wild Things Are

Dave Eggers: So here we are. It's always awkward doing this kind of thing together. If we wrote this the way we wrote the script, fighting over every word, it would probably take a year.

Spike Jonze: We should just have a conversation. Then we can fight over every word when we edit it.

DE: But let's be really eloquent. We can talk, and then after we transcribe the talk, we can make ourselves seem articulate.

SJ: Yes, we shall do that. It brings to mind something the bard once said: "Tis excellent to be spontaneous, tho better to be brilliant."

DE: He didn't say that.

SJ: He did. In one of his lesser-known plays, The Sisters of Hannah.

DE: So let's talk about Maurice Sendak, about the first time we saw him together. It was in the winter of 2003, I think. You and Maurice had known each other for a long time.

SJ: I had known him for about 10 years before we started making the Where the Wild Things Are movie. I had gone to his house in Connecticut many times, because initially we were talking about doing a movie based on Harold and the Purple Crayon, which was another book I loved as a kid. He was the trustee to the estate of its author, and so I needed his approval to do that movie. That movie never happened, but Maurice and I became friends. And, somewhere along the line, he and I started talking about a Wild Things movie.

DE: When you and I finally went up to Connecticut to see him, we were bringing in our general idea of how to do the movie. You and I had only been working on it for a few months, but I hadn't met him, and we wanted to give him a general idea. It was a very cold day in December, and we drove up from New York. I remember being really nervous. I had idolised the man since I was about four or five. He was one of the first authors whose name I knew.

SJ: That was a good sign for the whole process, the fact that you knew his work so well. So I wanted you two to meet, and I wanted you to get a feel for him, and feel the support from him that I felt. I knew you guys would hit it off.

DE: I guess he already had a sense that you were not going to do a typical adaptation.

SJ: I'd spent the previous six months forming the ideas I wanted the movie to be about, taking notes and thinking about who I wanted to write it with, finding you and getting you on board with it. So I had all the basic elements together. But before we actually wrote it, I wanted to present our ideas to Maurice. Do you remember your first impressions of meeting him?

DE: I was struck by how strong he was. He must have been 76 when we met him, but he was razor-sharp and very funny. He's a hilarious guy, incredibly vibrant. We walked in, and he showed us some of his Disney collection.

SJ: He has these insanely rare Mickey Mouse figurines from the 30s – before they corrupted him, as Maurice says.

DE: The rest of the house was very much like a regular person's house, wouldn't you say? I guess I'm always surprised when artists like Maurice have normal houses.

SJ: Yeah, I would say that. It's a very . . . what's that style of architecture? It's like a New England style. Very conservative. Is it a farmhouse?

DE: It looks a little bit like a farmhouse, in a sort of woodsy area. I think it was during that first meeting that he told us about that shed in the backyard. It's sort of like a stable, and kind of falling apart. I guess one of his neighbours complained about it being an eyesore. Maurice lives in one of those neighbourhoods that used to be all country houses, where people kept horses and were actual farmers. And now it's all yuppies who are making this suburb tidy and just so.

SJ: Yeah, they've built all these giant, 10,000 sq ft mansions that Maurice is violently opposed to.

DE: One of the neighbours complained about this "eyesore" farmhouse . . . And said he'd personally help remove it, if Maurice so desired, thinking he was being a big guy to help the old man get rid of the eyesore. And Maurice told him if he ever mentioned it again, he'd turn that stable into a whorehouse.

SJ: That was the last time that neighbour talked to him.

DE: That was when I was sure we would be kindred spirits. It was pretty obvious that we all had kind of the same impatience for that kind of just-so mentality, the sort of person who scrubs clean anything distinct in art or nature or a neighbourhood. So it was pretty obvious that he'd be OK with us making something distinct from the book.

SJ: He had just seen a pretty unfortunate adaptation of a friend's book.

DE: Yeah, it was similar to Where the Wild Things Are, in that it was another classic book that was very original when it came out, and it had been adapted in a very large, Hollywood way. Maurice was very candid about it. He said it was grotesque.

SJ: "Soulless."

DE: Right, "soulless". I think that was the operative word he kept using. What was interesting to me was how candid he was. Sitting around his dining room table, it was immediately clear that here is a very opinionated guy that would support us if we stayed true to the ideas we were talking about, and would only be a thorn in our side if we went a safe route. Did you already know he was like that?

SJ: I'd known it, because he'd been as blunt as possible on the phone. But to actually go to him with ideas that deviated from the book, and then have him say he respected that, is another thing.

DE: So there we were, sitting at that dining room table, giving him the basic gist of what we had in mind. Did we already know that we weren't going to have Max's room actually change, like it does in the book, and instead have Max run away from home, and get on an actual boat to sail to the island?

SJ: Yeah. That was actually the only thing that Maurice and I ever disagreed about in the process of making the movie.

DE: It's funny that he was the first of many people who objected to the room not changing into the jungle.

SJ: But even in that first meeting – when we were a little heated about it – he'd always go back to, "Well, it's your movie, you have to make what you believe in."

DE: He definitely wasn't shy about letting us know the things he really didn't like. He can be an intimidating guy. He's incredibly smart and astoundingly eloquent, but he really understood this being your movie. But he fought us on that bedroom part. I think at some point, it might have been then or later, he even proposed a compromise on that bedroom scene, where the room would still change, but that Max would climb out the window on a vine.

SJ: Yeah! He did suggest that.

DE: But it seemed like the idea of the movie being real and really dangerous would require Max to actually be in a forest and on a real boat. Because if he just goes to his room, we know everything that follows just takes place in his imagination. And then there's not as much at stake for the next hour of the movie. We really wanted it to seem like a small boy actually sailed across the ocean and, when he was on the island, that he was truly in danger of being devoured. That there was real fire, and real dirt, and real snow.

SJ: Maurice was struggling because – as much as he said, "I want you to make it yours" – he had lived with the book as his creation for 40 years.

DE: But I think that at that meeting it was really clear that we were going to take Maurice at his word. He realised the movie was going to be a combination of his childhood and your childhood, and maybe a bit of mine, too. So a lot of the themes were going to be brand new.

SJ: He based the book on themes and feelings from his life. I was picking up the baton. He and I would talk about what the book had meant to me as a kid, or had made me feel like. I would say, "You and I had very different childhoods. There were times when I might have been more sensitive to something than he would have been as a kid." But we didn't want to make Max a . . . a . . .

DE: A wuss like you were, yeah. (Laughter.) Most kids in modern movies are de-fanged. They have no wildness. What you and I and Maurice all figured out pretty quickly was that we all remembered what it was like to be an actual boy. We didn't pretend that boys wore three-piece suits to school, sat with perfect posture, said please and thank you all the time. We wanted to make sure that Max acts like a real boy – breaking things and throwing tantrums, the kind of kid who would play with swords and slingshots. When I was a kid, I was pretty wild and got in trouble like Max. And you had, and Maurice had been that way, too. We also established the movies we thought had represented childhood accurately in the past. We talked about The Black Stallion, My Life As a Dog, a couple of other movies . . .

SJ: The 400 Blows.

DE: Movies that didn't look down at a kid, but got inside him. And actually there are so few. It was kind of exhilarating, in a way, knowing how wide-open that playing field was.

SJ: Were you worried going into it?

DE: Meeting Maurice was an earthquake in my life. Meeting a guy around 80 who's still so full of fire – and if anything, had grown more authentic as he got older. We had yet to write anything for him to critique, so that gives you this great fear, like, "Holy crap, what's he going to think when we write this?" Because here's a guy who won't sugarcoat what he says.

SJ: He never did, for the next four years.

DE: When we left that day, there were big hugs and even kisses on the way out. He's very affectionate. I remember being struck by how full of love he was.

SJ: I think he was also really excited that you were coming on. He'd read your first book and loved it. It was another sign that the movie wasn't going in the typical direction of Hollywood development, where you're bringing on the "ace" screenwriter of the last big children's movie.

DE: He's had a lot of those people thrown at him throughout the years. He would always tell these stories where he would do imitations of the people who came to see him and what they said. "Mr Sendak, let me tell you how movies are made . . ."

SJ: "Mr Sendak, this is how you make a film for children . . . " or "This is what children like, Mr Sendak." When he does one of his imitations, look out.

DE: Oh man. Driving back to New York, it was snowing. It was like some kind of blizzard, windy and snowy. There were people pulled over everywhere, and we were just driving, recounting every minute of the day.

SJ: I remember being excited. It was like a relief, a weight off our shoulders. Driving home, I just felt like we had a wind at our backs. We went into the unknown, and it was Maurice behind us, pushing us with force in that direction. We had no idea where it was going to take us.

This is an edited extract from Heads On and We Shoot: The Making of Where the Wild Things Are, published by It Books. The film is released on 11 December.