When seeing the names Bill Hader and Kristen Wiig, you’d be forgiven for thinking only of their comedic work. Hader has popped up on every American TV comedy from 30 Rock and The Office to Portlandia and The Mindy Project and even lends his voice (and pen) to the crazy world of South Park. Wiig’s work in Bridesmaids, Imogene and Friends With Kids has allowed drama to seep through the comedic cracks, but the pair remain synonymous with their time on Saturday Night Live.

This week sees the release of one of 2014’s very best, The Skeleton Twins, also boasting one of the year’s best performances in Bill Hader’s Milo. Focusing on Milo and his estranged twin sister, Maggie (Wiig), the pair find their paths crossing for the first time in a decade after conveniently cheating death on the same day. What follows is a bittersweet and often heartbreaking journey as the siblings try to figure out why their relationship went so wrong. But don’t fear, it isn’t all sadness and tragedy – the film is as hilarious as it is poignant.

We sat down with director Craig Johnson ahead of the film’s European Premiere back in June to discuss how hard it was to get his sophomore feature made and just how much fun was to be had sitting back and watching Hader and Wiig do what they do best.

Anna Faris’ name was originally bandied about for the role of Maggie, but it’s hard to imagine a better pairing than Kristen and Bill. How did the two come on board?

Well, we had Bill on board and that is fully my casting director Avy Kaufman, because I love Bill on Saturday Night Live, but have never seen him do anything subtle or dramatic, or heartbreaking, or anything like that. And she had seen him in a table read of a dramatic script of a movie that never got made, opposite Kate Winslet and Bradley Cooper and Greta Gerwig and Paul Dano. And she said, out of that crew, Bill was the one who moved her to tears and that she found to be the most moving and that I should meet him. So I met Bill at a bar and I didn’t have him read a word from the script. We just sat and had a beer and there was just something about him in real life and when he wasn’t doing his impressions and being the SNL guy that, to me, infused the character of Milo with something completely new. Bill is a big film geek, he’s a little nerdy, you know, and suddenly I had this vision of Milo as this failed, sketch comedy nerd guy that helped me take the character to another level. And so after that meeting I walked out and was with the producer and we were just like, “no-brainer.” That was him, that was Milo. There was never anybody else, really. I mean we talked about lots of other people, talked about other actors including Anna. And we’d had Bill attached for years and years and years as we tried to get the movie made and as we were trying to find Maggie. I think I avoided thinking about Bill and Kristen because of SNL, and so I didn’t even give myself that as an option, because I thought, “oh, could that be gimmicky, or what not?” But the second I sat down and really thought about it I was like, “wait a second…” It was like a thunderbolt – this is what might make the movie special, this is what will infuse it with a chemistry that I can’t invent. And the fact that them as a duo exists in the public’s mind already will only help, because we are recontextualising them so much, you know?

Your co-writer Mark Heyman is best-known for working in the world of Darren Aronofsky, which isn’t particularly cheery! How did your allegiance come about?

It predates Aronofsky! Mark’s one of my best friends, we went to film school together at NYU, we were at grad school and just got on famously. We liked the same kinds of movies and so we said, “let’s write a movie together!” We knew the tone of the kind of movie we wanted to make. At the time, movies like The Squid And The Whale were coming out, a movie by Miranda July, Me And You And Everyone We Know, so a bittersweet, funny, a little offbeat, emotional. But we didn’t know what we wanted to write about, so we just started throwing out ideas from our own lives and that eventually built into The Skeleton Twins. And so we wrote the first draft of the script eight years ago when we were still in film school, and then it just sat in a drawer for a few years. He went off to work for Darren, and he’s always had more of that freaky, weirdo vibe as well that then worked really well with Darren’s stuff – a darker sensibility. I went off and made my first feature, a little indie called True Adolescence with Mark Duplass. And then after two or three years later I dug out the script, dusted it off and re-read it and it was like, “this is not bad! But it needs work!” And so we started tooling it up, and I took some passes on it on my own and thought maybe I could get this made now because I’ve made another movie, and it took a long time, but eventually we did it.

Your script genuinely cares about its characters, which is something we don’t get to see that much in mainstream cinema. Is that something that really frustrates you?

Absolutely! What makes me mad is there’s no reason for that other than laziness. You know, I’ve worked in the studio system and there’s just a lot of things going against you that even though everyone talks about, “oh, this has got to be about the people, it’s got to be about the characters,” there’s so many other influences – I’m talking about Hollywood movies right now – that just make it almost impossible to focus on what the movie actually needs, which is the character’s story and the character’s journey. And also, the bigger the movie gets, budget-wise, genre-wise, the more scared people are about nuance in character and the more people are scared about ambiguities. Especially any moral ambiguities in the characters, people are so scared he’s not likeable! And that was why it took this movie forever to get made and we would submit it to production companies that do even darker stuff and they’d be like, “we love this movie! Oh it’s so complex, it’s funny and it’s emotional. We’re not going to make it – it’s a little too dark and weird for us, but really good luck! We know it’ll get made some day!” Everyone said that! Until you finally find this weird combination of people who are willing to take a risk on you.

You mentioned Mark Duplass earlier. How hands-on were Mark and Jay Duplass in regards to this process?

You know what, they were pretty hands-off honestly on this one. Mark’s a really dear friend of mine and he was kind of like a film mentor. What Mark was critical in doing was, when he stepped on to executive produce it, he legitimised it. We were able to get Avy Kaufman because Mark knew who she was and was able to ninja kick that door open for us. So in terms of a catalyst, Mark was really the catalyst to getting this film off the ground, and then was there whenever I had a question, I would check in. So it was just sort of like, “oh, he’s looking over my shoulder, it’s like a movie guardian angel!”

How much of what we see is improvisation? Did you let Bill and Kristen go and play, or is there a lot on the cutting room floor?

Yes. It was all scripted, however there’s lots of improv in it. I just like improv. And there’s no way I’m going to make a movie with Bill Hader and Kristen Wiig and not let them improv! Because they’re so good at it! And so sometimes I’d have them just stay on script, but then maybe by take two or three I’d be like, “maybe just do the vibe of the scene, put it in your own words.” I would almost always encourage them to just curlicue off in moments as well and throw in anything. I wanted them to not feel at all burdened by having to stay rigid. I just think it frees actors up, they feel less obsessed with getting things word-perfect, and it just makes everything feel more natural and more authentic. And then there were definite bits, the dentist’s office, where I just let ‘em go! I think I had even written in some bits, none of which were in the script – I think the stuff that’s in the actual movie was nothing like what I’d written, it really was just let ’em go. And there was hysterical stuff they did, in the dentist scene, say, in particular, that we had in earlier versions, but what was so critical and so important to me – because we knew the tone of the movie was so tricky and we knew that if it tipped over too much into comedy, it would take us out of the real feeling of a brother and sister. And then on the other hand, if it tipped too much into dark drama, suddenly it would just be a slog. So keeping that balance was critical. And so in that dentist scene there are some hysterical moments – maybe they’ll be on the DVD – that we cut out because, you know, they were starting to feel a little bit too much like two professional comedians improvising together and we had to be real careful in that calibration, because you also don’t want to cut out your funny stuff! But you had to believe this was brother and sister on nitrous and not two professional Saturday Night Livers.

Luke Wilson is in the mix as well, and he will unfortunately go slightly underappreciated seeing as he is sandwiched between two powerhouse performances! But he is so great in that role. What was it like working with him?

Thank you! I loved Luke from the Wes Anderson years and then hadn’t seen him in much recently, and I did watch, when I was thinking about casting him, the first season of the HBO show Enlightened, the show with Laura Dern. It’s a fantastic show, it’s so good. It’s only two seasons and got cancelled, but I totally recommend it. Luke is a prominent role in that and plays her ex-husband and he was so good in it. And I was just like, “oh man, Luke is really great!” So when Luke came on, he was amazing. What I didn’t know about Luke was that he is a killer improviser. And Bill and Kristen were just jaw dropped at how hysterical and just yet very real all his improvisations were. Some of the funniest and most real stuff that comes out of that Lance character was Luke just riffing on things a little bit. The character was there on the page, but he brought from an improv point of view a real humour, a real sweet sort of Labrador Retriever humour, you know, this kind of nice dude who’s maybe not the sharpest tool in the shed. But boy, is his heart in the right place, and boy, is he a good dude. Luke, you know, what can I say. That’s what he brought.

The Skeleton Twins is released in UK cinemas on Friday November 7th. You can read our review here. Photo by Steve Jennings/WireImage.