Director Neill Blomkamp's third film, Chappie—about a sentient police robot in a near-future Johannesburg overrun by crime—hits theaters today. We sat down with Terri Tatchell, Blomkamp's partner and co-screenwriter, to talk about script changes, writing for non-actors, and how to make robots sympathetic.

Chappie was inspired by a short. How did you and Neill develop the idea further from that, and how did it evolve as you were working on the script?

When Neill made the short [in 2002 or 2003], it was specifically to get himself repped to do commercials—it’s not like we looked at the short and said, “What can we do with this?” There just happens to be a policing robot in that commercial. So we didn’t approach it in a way of doing an adaptation. Neill literally woke up one morning, came down the stairs, and said, “I have this idea.”

At this point [after co-writing the script for District 9], we were never working together again, ever, ever, ever. And he’s always pitching ideas, every single day—he’s so fun to be around because he’s always got different ideas. Usually, I’m like, “That sounds great,” but this one, he didn’t even make it down the stairs. I’m like “OK, time out on the not working together—I need to work on this with you.”

[We wrote] the first draft in three weeks, and we re-wrote it again to set it in LA—because there was a point where we didn’t think we were going to be able to shoot in Johannesburg. That took a little bit longer, just because it wasn’t right. I still liked that version—it had the same players coming to LA, but then they [moved] it back. I would say what ended up on the screen is pretty much exactly what that first draft was. It was one of those, I think, very quick easy processes that you’ll never experience again in your life. Even re-writes or changes felt kind of easy.

When you and Neill were working together on a script, what is the process like? How does that work?

That process is kind of funny. With District 9, we would be locked in what we called our bell tower in New Zealand. Neill’s very calm, and I’m very heated, and I’d wake him up in the middle of the night with ideas—and he can’t stand that. He’s like, “I do not like your work personality.” [Laughs] So, now, we e-mail. We do not write together, in the same room, ever. Sometimes if I really want to prove a point, I will go into the bathroom when he’s in the shower, and I’ll sit in there and be like, “Just say we can do this!” And he’s like, “Yes, just go away!”

Neill really wanted Die Antwoord’s Ninja and Yo-Landi to be in this. Does writing for non-actors change the process of writing a script?

No. It was them from Day One. I think if you have real people in your brain being a character, in a way, it sort of writes itself, so it was very easy. When we had to transpose them to LA, in that draft, their part was still really easy, [but] explaining why they were in LA, that was a little bit harder … They just belong with Chappie. Maybe, if you’re writing with a non-actor in mind, you don’t have other roles in your head, it’s just that character—that may be the key.

What you’ve chosen to make a movie about is not an easy topic. You’re not only exploring what it means to be human, but you’re dealing with really complicated scientific areas—robotics and artificial intelligence. Did you do any research into that while you were writing?

I find it fascinating, but probably in a less scientific way. I am more curious in how people will respond, and how it would affect individual lives. And I’m very curious about—right now there are such different views on what it would mean to humanity. So the science behind it, I leave that to Neill. He’s constantly reading that.

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It must help, too, to not really be immersed in it, because then you can say, “Wait, I don’t get this.”

Yes. If I’m questioning something that’s in any of his films, I’ll say, “OK: curtain, bum in the theater, let’s pretend,” and I’m wondering, does this makes sense, why doesn’t this make sense? With Chappie, where I was coming from, anyway, was so not based in science, that I really didn’t worry about that at all. I mean, I don’t want to poke holes in my own film, but there’s suspension of disbelief.

It’s always walking a fine line between wanting to have some kind of science in there, but it’s a movie, so it’s not like you’re super beholden to it—but it’s always interesting to me to see where people get that kind of information from, and how it’s incorporated. And there are some pretty heady topics and themes—the whole idea of “what is consciousness?”—that are very well conveyed …

It’s kind of in your face, for sure. The theme that I really love, that Neill doesn’t particularly love or see in it, is violence. As a mother, it’s like, where [does] violence come from? I feel like each character in the film has their own little arc with violence, and that I had fun exploring.

Obviously, a lot of the reason that we empathize with Chappie, and why we love him, is Sharlto’s performance, and what the visual effects artists were able to achieve, which was incredible. [Copley wore a performance capture suit and performed with the other actors; the visual effects artists overlaid him in the scenes with the digital robot.] Were there certain things you wanted to do, from a storytelling perspective, to make sure the audience loved the robot?

Chappie evolves as a child, and an innocent. I really, really like films that have unlikeable leads, like Vicus [in District 9]. He’s incredibly unlikeable, and so we had to be very conscious about making sure the audience didn’t hate him. And that was never the case with Chappie. The other characters in the film, absolutely. But Chappie, and I think it’s because of his curiosity, and his love of life, and his enthusiasm, and his innocence, and I think he’s just a character that hopefully will touch everyone in a different way, maybe. There was never a worry that people wouldn’t like Chappie.

There’s one scene with a bunch of kids who are throwing things at Chappie, and it’s so hard to watch.

As the visual effects got better and better in that scene, it was more painful to watch. It’s pretty heartbreaking.

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What was your favorite scene in this script, and what was your favorite part to see come to life?

One of my favorite scenes wasn’t in the script. I was on set for a week, and then I was back home in Vancouver opening a restaurant. But dailies got piped in every day, and so I’d watch the scenes, and I’d give Neill any thoughts if I had them. The scene that I love was Chappie with the Barbie behind his back. It’s probably because it was a surprise to me.

Were there any other moments of surprise? It seems like, when you’re doing something that’s this VFX heavy, that there isn’t necessarily a lot of room for improvisation.

There wasn’t. Neill was very by the book. He did not want improv in this case.

Every day I would watch it, and be amazed that everybody was making sentences that I had heard in my head over and over again sound better than they did on the page. And that is, as a writer, is a gift. I love the scene with Yolandi and Chappie in bed, reading Black Sheep, just the little nuances of the way she delivers the lines, and the way he tilts his head and thinks—stuff like that, you can’t write.

You and Neill have a daughter. Were there any moments from her childhood, or funny things that she did, that you wrote into the script?

There are moments in there, that Neill wrote, where I hear how he speaks to her, and it's like, "aww..." I don’t know that you’re ever aware when you’re doing it. I don’t think, on my part, that I’ve put Cassidy in there as Chappie at all, but I would definitely say that there’s more of Neill parenting Cassidy in there.