The most hilarious, exhausting movie of the 21st century was, ironically, conceived as a cool-down. In the mid-2000s, Adam McKay and Will Ferrell were drained. The director and comedian, whose partnership dates back to their time on Saturday Night Live, had just finished Talladega Nights: The Ballad of Ricky Bobby. The hit NASCAR satire was shot on searingly hot and painfully loud speedways. By the end of production, the duo needed a break.

But McKay knew that the film’s biggest laughs were generated by Ferrell and costar John C. Reilly off the track. “I love the race footage in Talladega Nights, but the funniest stuff is in the pits, with them screwing around and improvising,” said McKay, who resolved to strip down his next project. “Let’s make sure it’s just in a house and a few locations with a bunch of really funny, great actors,” he recalled vowing at the time, “and we’ll keep it simple.”

And like that, Step Brothers was born. Released 10 years ago this month, the warped opus tells the tale of two full-grown man-children, played by Ferrell and Reilly, who live at home with their newly married parents. The delightfully absurd premise, lovingly shaped by a man who encouraged performers to go off-script, helped to create a kind of euphoria on set. One cast member positively compared the experience to dropping acid.

“Movies are such a controlled medium,” said New York magazine critic David Edelstein. Step Brothers is an exception to that rule. “I think what it represents to me,” the writer added, “is a kind of improvisatory freedom that you rarely see on screen.”

The surreal mix of filthy silliness and reckless abandon resulted in one of the most rewatchable big-screen comedies of all time. “What I think people respond to is this very dangerous edge in the whole thing,” said Mary Steenburgen, who plays the mother of Ferrell’s character. Appearing in it, she pointed out, was like“going wild.”

Making Step Brothers brought its cast and crew back to adolescence. This is the story of how moviegoers were transported to a world of endless riffing, best friends, junk food, sleepwalking, porno mags, bullies, bunk beds, and uncontrollable laughter.

Part I: “Wait a Minute, This Is Actually a Movie”

Adam McKay (director): I do remember saying to Will and John, “I just picture you guys in bunk beds.” And I was like, “Is there a way to have that?”

Brent White (editor): We’re cutting Talladega and me and Adam are working, and Will comes by, and John comes by, and I remember that they were saying, “OK, now what are we gonna do next?” There was no script. There was no idea. It was just, “What would be fun for us to do?” One of them says, “You know what would be really funny? Bunk beds.” And that’s all they said. And immediately in my head, I go, “I have to see this movie.”

McKay: The idea of grown-ups who still live at home. The bunk-bed image spread to that. In Europe it’s actually pretty common. Why couldn’t two single parents have older kids who still live at home? That’s when we were like, “Wait a minute, this is actually a movie.”

Will Ferrell (Brennan Huff): I could totally relate to this. I lived at home for three years after college. I had the benefit of a very patient mother who was like, “All right.”

McKay: This was an era where studios were just hungry for comedy. DVDs were selling like crazy. Ferrell got to that place where he was one of those big comedy stars. And then since I directed Talladega and Anchorman, I was now a provable director. Sony, who we were working with and having a good time with, they bought it off the pitch.

John C. Reilly (Dale Doback): We all kind of figured out the story together, Will and Adam and I.

McKay: Ferrell had this guest house off this old house. We would just go up there and write. At first it was Reilly, Ferrell, and I just laughing. We sat around for three or four days and just wrote scene ideas, images, attitudes, locations. “I would love to see a movie where bunk beds collapse.” “I want to see a movie where little kids beat the shit out of grown men.” I remembered a story from when I grew up where a kid on our block threatened a grown-up. Then the grown-up backed off. I remember being 12 years old, and being like, “Wow! Our friend Pat just threatened a grown-up and then the grown-up backed off!” We wanted that in there. John C. Reilly had a story of touching his brother’s drum set as a kid.

Ferrell: We were having so much fun. What would normally be a one-and-a-half-, two-page scene would often be 10 pages. The first rough draft came out at 180 pages.

McKay: You obviously can’t turn in a nearly 200-page script. So we had to seriously chop it down. But there are so many 20-, 30-page runs in the script that had to be cut out.

There was one run we had where Dale and Brennan’s dysfunction got to such a point. … It was in the middle of the night and somehow it’s mentioned that Dr. [Robert] Doback [Dale’s physician father, played by Richard Jenkins] keeps a pistol in his safe. Dale and Brennan are in bed, and Dale is scaring Brennan. And he was doing that thing where you get all wound up at night, listening to sounds, and Dale is scaring him. And then Dale starts to get scared, and they both get really freaked out and they convince themselves that there’s an intruder downstairs. And they shake Richard Jenkins and Mary Steenburgen awake, like, “There’s an intruder in the house, and he’s armed.” And so Dr. Doback goes for the gun in the safe and Dale and Brennan light off Roman candles in the house and Dr. Doback fires a round off in the chaos. Then the police are there and they say, “There’s no one here. There’s nothing going on.” And then Dr. Doback says, “This is so fucked up. This is so unhealthy. You guys have to get out of here.” And then basically Dale and Brennan are like, “Can’t we just go to SeaWorld?”

That’s somehow the answer: “Can we not be so angry? Why is everyone so angry? Why can’t we just go and have a nice time at SeaWorld?” And Mary kind of acquiesces. And then it’s this giant trip to SeaWorld. It’s the greatest day ever. The parents both just buy into the dysfunction and have this amazing time at SeaWorld—except that Mary’s purse gets snatched. It’s all a montage, and then they’re driving home with giant grins on their faces. And then all of a sudden, Dr. Doback hits the brakes on the car and he’s just like, “What the fuck are we doing?”

And I remember Ferrell and I had tears in our eyes at them freaking themselves out thinking there’s an intruder. I remember that run was, without exaggeration, like 14 pages.

White: Those ideas, they don’t go away. Anchorman 2 has a SeaWorld scene in it. That idea, if it doesn’t make it into the movie, it just kind of sits on the backburner and percolates until it’s ready for the right movie. That’s one of the great things that happens in this world.

McKay: The one question was: Are they screwed up? Is there something wrong with them?

Horatio Sanz (Billy Joel cover band lead singer): Are we looking in on some really, really dark mental issues? And then you get into The Three Stooges of it all.

McKay: We actually had a chunk in the original script where the parents were like, “What’s wrong with them?” and actually took them to get a battery of tests where it was like: Do they have a cognitive disability? Or was there emotional trauma? Really in the end, the doctors are like, “I’ve done all these tests. There’s nothing wrong with them.”

In this new world we live in there’s video games, free food, and 1,000 channels. They have no reason to leave the house. They’re having such a great time!

Part II: “It Got Really Dark and Really Gross, Really Fast”

When it came time for casting, the movie’s brain trust sought actors who could hang with Ferrell and Reilly, two freakishly tireless improvisers. Academy Award–winner Mary Steenburgen and eventual Oscar nominee Richard Jenkins filled the roles of Dale and Brennan’s bewildered parents. By no coincidence, the supporting parts—including Brennan’s chauvinistic tool brother, Derek, and Derek’s secretly intense wife, Alice—were played by up-and-comers who went on to appear in some of the decade’s best comedies.

McKay: I would warn every actor: “Before you take this role, I’m gonna have you improvise. I’m gonna throw ideas at you. We’re gonna mess around.”

Allison Jones (casting director): That’s a pre-rec for any of his movies, for sure. I think because I’ve done it for so long, I’m pretty familiar with everyone’s improv skills.

McKay: We kept coming back to Mary Steenburgen. She’s so sweet but she’s funny.

Mary Steenburgen (Nancy Huff): Will and I did Elf together, and we had a great time. He called me and said, “Would you feel insulted if I asked you to play my actual mom?” I think I’m, like, [14] years older than him.

McKay: The funny thing about Richard Jenkins—he has this look. He looks like a conservative dad from Pasadena.

Jones: Richard Jenkins has been funny forever. But he’s not trying to be jokey. He’s not the Chevy Chase version [of a dad]. It’s earnest and smart.

Adam Scott (Derek Huff): Getting the role was a total fluke. I hadn’t really done any comedy at that point. Step Brothers is 100 percent my foray into comedy.

McKay: Adam was the one we didn’t know as well. But [Step Brothers producer] Judd [Apatow] had worked with him. And Paul Rudd and Jon Hamm were friends with him. And Paul Rudd just told me: “Adam Scott’s one of the funniest guys I know.” And if Paul Rudd’s saying that, you know he’s good.

Jones: Nobody knew he would be that funny because he’s kind of low-key. His competition was pretty much—we had a lot of great guys read for that—Jon Hamm. And they were both frickin’ funnier than you ever thought they would be.

Scott: The thing I immediately thought of was the Robb Report. It was so long ago that I thought of a magazine. I remember going and buying an issue of the Robb Report and just looking at those guys. It was guys with suits on, on tarmacs in front of private jets, in their sports cars, in their sunglasses, with their slicked-back hair. They were super serious. That’s sort of where my mind went. It was really funny. All you had to do was put a little spin on it. I just remember in the audition, I think I called Mark Cuban “The Cubes.”

Brian Huskey (interviewer): I think I read with Adam Scott. A lot of the dudes that came in for that were kind of what you’d picture as sort of the snarky, money-centric douchebags. He just kind of looks sort of like a white guy. He did a really good job, even though the first impression of the guy might not be that he’s a douche. But within a few sentences, you’re like, “Oh my God, you’re so gross.”

McKay: God, he is so good at playing an A-hole. He had all these little, subtle moves that he was doing. In the room they’re not bowling you over, but they really played well on camera. Thank God we ended up casting him.

Andrea Savage (Denise, Brennan’s therapist): Adam Scott and I had just worked together, oddly, on the pilot of Party Down. When the show got picked up, I was too pregnant to do the role, and Lizzy Caplan took over.

McKay: Kathryn Hahn had done a small part in Anchorman. We knew she was amazing.

Jones: Kathryn was probably a no-brainer once she came in.

Kathryn Hahn (Alice Huff): Allison Jones is such a champion casting director. She had a very, very, very small room. It was [McKay], me, and John C. Reilly. And I had never met John. Boogie Nights! I was just obsessed. I remember I brought a bag. That was my little armor, I think. It was like my Dumbo feather. I didn’t think I could fly without it.

Jones: [McKay] likes to get improvisers to read with these actors so he can get them going. Brian Huskey read with the Kathryn Hahn role. He is this plain, normal-looking dude who you would recognize if you saw him. He’s done a lot of comedy. Brian is able to go from someone who looks like a math teacher to filthy.

Hahn: It got really dark and really gross, really fast. There were a couple of takes where we got really detailed on how to kill Adam Scott’s character. It was very To Die For.

Savage: With those auditions, for McKay, he kind of really wants to see what you’re going to bring to it, to elevate what’s already there.

Huskey: When you’re auditioning for something, a lot of times people think there is a right idea that you have to execute. I think the difference with McKay is there’s a right idea that maybe we can all figure out together. And if you go a little bit further, we can see what the boundaries are. But if you don’t go there, you’re kind of stuck with like, “That was cool. Um, all right.” Their whole model is, “Just fucking go crazy.”

Hahn: There’s this feeling where all of a sudden you bust through what’s expected and you just take off on this path with them. We went on forever on the weirdest tangents. I definitely walked out of there like, “I’m never gonna get it, but that was the most fun. I can’t believe I got to improvise with John C. Reilly.”

Savage: Improv at its best, you’re not trying to shine, you’re not trying to make a big deal about it. But I think because it was an audition for me, I felt the need to do a little bit more. It takes a little time to figure out how to work with the person you’re going to do it with. And so because I’d never met him and because it’s Will Fuckin’ Ferrell, Jesus Christ. I just remember getting distracted and being like, “Oh God. Look at him.”

Logan Manus (Chris Gardoki): I got an audition. My acting coach at the time, he told me, “This is a Judd Apatow production. So when you go in there, just be completely over the top. Be as crazy as you can. If there’s a chair in the room, flip the chair. Throw a huge temper tantrum.” Here I am, like a 13- or 14-year-old kid, and I looked at him, and I was like, “What?” And he said, “You heard me, go in there and just lose your mind.” My mom was driving me there and I told her what he said and she looked at me and said, “Well, if he told you to do it, I mean you may as well.”

So I go into the room, and it was a kind of do-or-die moment. And we get halfway through the famous playground scene, and at the time the script was a bit different. I went up and got in [Brennan’s] face before I punched him. So I walked up and kind of acted like I was getting in his face, and started screaming, and started throwing my hands in his face, and started doing all this crazy stuff. I jumped up out of the chair I was in. I kicked the chair over. And for a minute, I walked out of the room. The only thing I could think to myself was, “Either I’m never getting called back to this casting office or I just did really well on this audition.”

I got called a week later and [was told], “You booked it.” I was really happy about that. I asked Adam McKay about [the audition] and he said, “As soon as I saw the tape, I knew I just had to have you.”

Jones: Gillian Vigman did a great, filthy audition for [Alice]. And we liked her so much we gave her a part. It was the part where she said her name was Pam and Will Ferrell kept calling her “Pan,” and she kept going, “No, Pam.”

There are people that Adam loves and I love. [Rob Riggle] came in. Those parts are always underwritten, and then they steal the movie.

Savage: It was a great group of people they got. The table read was so funny. It just crushed.

Gillian Vigman (Pam): I think Kathryn Hahn was unable to go that day, so I did her role. I was wearing a dark shirt—and I felt so bad, but it was a big table read, so you get nervous—and I’m not a big sweater, but I’m sweating as if I’m going through labor. I would look at Andrea and be like, “What is wrong with me?” I was screaming laughing, which is so inappropriate as a reader. But I couldn’t stop.

Part III: “They Looked Like Overgrown 11-Year-Olds”

For the cast and crew of Step Brothers, the experience of collaborating with McKay, Ferrell, and Reilly led to a high that they’re still chasing today.

Savage: Not to kiss up, because the last thing I want to do is make Adam McKay feel good, but he is the funniest person I’ve ever met. I will say that until the end of time. He makes you feel like you’re just hanging out at a party, making jokes and doing bits with your friends.

Sanz: Me and McKay ended up being in the Upright Citizens Brigade, the first incarnation with Matt [Besser] and Matt [Walsh]. So that’s the [early] ’90s. Then he got hired by SNL as a writer, and then a year or two after that I got a chance to audition.

When I met him I realized that he’s a good sparring partner. That was instant. I thought he was gonna be doing movies maybe like Bill Murray–style. Because he was certainly talented enough. I think maybe he didn’t have the Hollywood look, so he was like, “Eh, fuck it,” and then realized it’s less demoralizing being a writer, and he got rewarded for it really quickly at SNL. I think he never looked back.

Steenburgen: He’s the third brother.

Vigman: He can go from something that is very high-minded intellectually to something like this, that may be considered silly in base, but really, there’s a high intelligence behind it.

Reilly: Adam McKay and Will Ferrell, they’re both really subversive guys. Subversive and incredibly intelligent. I think that’s one of the reasons I started to work with Will and Adam.

Savage: What it is is just ridiculous humor, but done in its most elevated way. And there’s a subversiveness underneath it. I feel like that’s sort of Adam McKay’s specialty and Will’s. Just their best things are when there’s a little bit of like a “Fuck you!” underneath it. Like, “We know that we’re being ridiculous.”

Ken Jeong (employment agent): You just got the sense that they were this three-headed monster. A backcourt of like, Kevin Durant, Steph Curry, and Klay Thompson. They’re unselfish and they share the ball. “Oh my God, those guys are scoring so much! Oh my God, they’re gonna pass the ball to me and let me put in a layup because the defense is gonna collapse on them!” I’m literally a doctor and I just banked in a layup.

Scott: I just want to make clear how cool Will and Adam and John C. Reilly were. You feel like you’re in immediately. You feel like you’re being supported. It’s a really warm, lovely atmosphere they create.

Scott Maginnis (prop master): My youngest daughter, who must’ve been 3 at the time, she refers to [Reilly] as the guy who does the bunny impersonation. Because the first time he met her was on the set of Step Brothers. She goes, “Hi, John!” And he said, “Hang on a minute.” And he goes around the corner and he comes back out hopping, doing a bunny impersonation. He’s like a big kid.

McKay: Playfulness and humor mixed with incredible specificity. That’s what Reilly has almost as much as anyone walking around. I don’t know if you saw the [latest] King Kong movie. He’s fucking fantastic in it. The jokes he’s doing are really specific. The whole movie wakes up when he walks in. His instincts are so good. Even when he’s doing the broadest joke in the world, he always makes it specific and personal. And that’s really the key to great comedy.

An example of Reilly’s specific genius comes when Robert and Nancy announce that they’re divorcing, and Dale blurts out, “Is it ’cause we were bad?”

Scott: I was there. He was really crying. Those guys aren’t fucking around. He and Will, they jump in and they’re really doing it.

McKay: You’ve gotta understand what a machine Ferrell is. Ferrell will crank for hours. He will go. He never complains. He’s a horse. He will work all day long doing the craziest things.

Vigman: They were meant for these roles. They looked like overgrown 11-year-olds.

A.O. Scott (New York Times critic): They’re just perfect. Everything about them, their big soft bodies, they really do look weirdly 8 years old, even as adults.

Huskey: On a physical level, they are gigantic people. You have these two gigantic talents who are housed in these gigantic physicalities.

Susan Matheson (costume designer): I ended up with racks and racks and racks of vintage T-shirts that could harken back to when they were in elementary school. There’s even one that John C. Reilly wears that says “Spring Break ’84.” There’s another one that says “Life is a Beach.” And I thought it was so silly and juvenile and I thought, “Well, what’s more perfect than sending Will Ferrell wearing that shirt to therapy with a therapist that he’s in love with?”

Savage: John C. Reilly, he just killed me. He labeled me “Demandrea” early on. Not because I was demanding. He just thought it was funny because I’m not demanding. He would always give me shit.

Manus: We were cutting jokes, talking trash about each other. Here I am, just a random kid who’s in the movie, and they were cutting up with me like they had known me for years. We were talking about going paintballing. We were talking about Halo 3.

Just to give you an idea of kind of the relationship that Will and I had at the time, I actually did Land of the Lost about a year later, and there was a scene where we had to smash up a car. I was standing on top of a car and had to kick a windshield in and put my foot through it. It was kind of a nutty scene. We were over at catering getting lunch after, and Will just so happened to be in front of me, and I said, “Hey Will,” and he turned around and said, “Yes, Logan,” and I said, “Just so you know, the whole time I was smashing up that car, I was imagining it was your face.” He looked at me, and I’ll never forget it, he said, “I’m very glad I could be of assistance to your acting career.”

Part IV: “It Gives You a Comedy Boner”

The process of filming was entertainingly unpredictable. Steenburgen said that her husband, Ted Danson, never joins her on movie sets, but made an exception for Step Brothers.

McKay: It’s not like I’m some spiritual guru when it comes to improv. Really there’s one trick, which is: You gotta let everyone know they can do shitty stuff. So as long as you know you can do stuff that’s not funny, stuff that doesn’t work, stuff that’s offbeat, instantly the improv gets like 60 percent better. So I’ll say it over and over again the first fifth of the movie. I’ll just be like, “I don’t care. Just try it. It doesn’t matter. If it’s not any good, we won’t use it.”

Savage: He’s a good laugher. So he always makes you feel good. He’s just always in a good mood. It makes it a very safe environment, especially for people who don’t do a lot of improv. Because he’s laughing.

Rob Riggle (Randy): To Will and Adam’s credit, they let us play. When I made that, I was pretty new to feature films. You still get nervous and everything, but they still let me swing for the fences and do crazy shit.

Adam Scott: I remember Kathryn and I the first day just sort of looking at each other like, “Oh my God, this is the best gig.”

Hahn: It definitely felt like I had someone there that I could turn to and be like, “Holy shit, can you believe we’re doing this movie?” Because everyone else I felt like I had to be real cool around. Every so often we would look at each other and be like, “Oh my God, that’s Will Ferrell.”

Adam Scott: The last thing I had done was this HBO show Tell Me You Love Me, which was a super dark relationship drama. And so I was sort of looking around being like, “What the hell?” And with the improvisation, I was completely lost. I was there with Will Ferrell and John Reilly. Like, I didn’t know what the hell I was doing. Truly. When I say they really were generous to me in the editing room, that’s not an exaggeration.

It was like learning how to do the shot put at the Olympics in front of a stadium filled with people and cameras and judges.

Steenburgen: Richard and I, literally day one, looked at each other like, “Holy crap, how does one do this?” I love comedy and I love improvising, but we’re talking about savants. We both had to take a deep breath and realize that’s not what we’re hired to do.

Richard Jenkins (Dr. Robert Doback): I don’t have any improv experience. It doesn’t mean I haven’t played around with scenes and things like that, but these guys are really fast. It’s been an incredible test.

Steenburgen: I knew that it wasn’t my job to even remotely compete with that. It was actually just the opposite. My job was to try to make some sort of a reality out of the fact that these two adult people were living with their parents. I had to make that real. It was more important than making that hysterical. The more real I could make it, the funnier, hopefully, the whole thing would be.

McKay: They both kind of picked up on the whole game of what we were doing. [Jenkins’s] reads would just kill me. The one after [Dale and Brennan] wreck his boat: “You goon!”

Steenburgen: When Richard would get apoplectic, that to me was one of the funniest things of all.

McKay: Steenburgen had a great line, too, where Ferrell kept insisting that he and his therapist were dating. Savage just said some line like, “You are an enabler.” And then Mary just leaned in at the moment and said, “You are a keeper!”

Vigman: The more dramatic it is, the funnier it is. It makes it better when something is so fucked up but they’re playing it as grounded as possible. Oh my God, it gives you a comedy boner.

Jones: [McKay] understands that these guys are frequently funnier than whatever a writer comes up with. He just shouts stuff out on set and the actors are good enough to riff on it.

Sanz: He’s such a fast, smart dude that he’s just spitting out alternate lines almost all the time. Those alternates make the crew laugh.

Steenburgen: Adam loved to just scream off-camera obscenities for me to say, for some reason. That was totally delightful. The filthier the things that would come out of my mouth, the more Adam loved it. The scene with [Dale and Brennan fighting with] bicycles. There’s people all over the neighborhood watching, and Adam’s screaming, “Mary, say, ‘What the fucking fuck?’” You had to wait for all the people in the neighborhood to stop laughing. And I say it, and they start laughing again.

Adam Scott: I didn’t know that this even was allowed. I was like, “Are we breaking any rules or laws here?”

Manus: Adam came up to me and said, ‘Hey, you wanna make me happy?” And I said, “Yeah.” And he goes, “Kick [Ferrell] as hard as you can.” So I said, “OK, that’s easy enough to do.” I had done some Muay Thai and karate for years before that, so I brought that kick back and I let him have it right into the back of the knee, and then I start wailing into his stomach, and my dad just so happened to be there the day we shot that scene and he came up to me and he said, “Logan, you do know you don’t have to hit him that hard. Just act. This is called acting.” And I said, “Dad, the director told me to.”

McKay: We just finished this Dick Cheney movie with Christian Bale. Christian Bale is jaw-droppingly good in it. There were several moments when we were filming where you get goose bumps. And there are some other really good actors in the movie, too, like Amy Adams. When they finish their scenes, you’re like, “Holy crap.” Someone asked me, “What are some times on set where a scene happens and just spontaneously, everyone knows it’s great?”

The big one I remember was the first take Kathryn Hahn did where she comes at Dale in that doorway and is like, “I want to roll you into a little ball and shove you up my vagina.” The first take she did of that, when I said “cut,” the whole crew spontaneously applauded. I remember Mary Steenburgen came over and gave her a hug and said congratulations.

Hahn: I was in such a fugue state. That might’ve been one of my first scenes. So that in itself was terrifying. I think because I was treated as an equal, I was able to have that kind of fearlessness. If there had been somebody wringing their hands behind the monitor, or shaking their head saying, “No, uh uh,” then I would’ve been totally stuck in my head.

McKay: I’ve never seen anything like it. It was such an electric, special performance. Forget that it was comedy. It really was one of the great performance moments I’ve ever seen.

Matheson: Being on set was like a drug. It was like watching your own episode of Saturday Night Live, but even better, right in front of you.

Steenburgen: People always think they want to come to film sets, and then they get there and they see the same thing over and over, so they leave much sooner than they thought they were going to. But not that movie. Adam had to move video village so far from the set so he didn’t ruin every take from laughing. Also: The audience that would be at video village would ruin the takes.

And then there was me, who was by far the worst giggler on the set. Somebody once told me that they had a drinking game where they drank every time they could obviously see me laugh. And I asked Adam, “Why did you keep that take?” One of them was the sleepwalking scene, and I’m starting to laugh. And he goes, “Mary, we don’t have any that you weren’t laughing.”

White: There’s this other version of this sleepwalking scene where [Dale and Brennan] get up and they get in a car and they drive to a convenience store and they beat the convenience store guy up and tear up the gas station. Then they drive home and hit a fountain in the neighbor’s yard. And they wake up and they have no memory whatsoever of what they’ve done, but they’re just covered in junk food. It’s super funny. But it was just so long that it couldn’t physically be in the movie.

Matheson: There are so many good takes. You start begging Adam: “Please leave that one in!”

Hahn: You feel like, “Holy shit, I do not envy the editors trying to find a story through all this.”

Steenburgen: It tended to be mornings scripted and afternoons playing with what was mined in the mornings.

Riggle: We’d die laughing, and then they’d go, “Let’s do it again, but try this or try that.” Randy is an obnoxious character. I realized Adam [Scott] was making these great points and I’m his henchman, so to speak. Anytime he said something, I just wanted to punctuate that, so I’d go, “Pow!” in Will’s face. Basically, it was Adam Scott and I and Will just screwing around.

Jeong: My scene with John C. Reilly was I think maybe 30 seconds. I find a temp job for his character to get to Catalina Island for the third act. It was just a one-minute scene and quite frankly if I were directing it, I’d be like, “Look, we gotta beat the clock guys, let’s just get this out in 20 minutes so we can get this in before lunch, I am starving.” We did that scene for three hours.

Steenburgen: There’s a scene that Will Ferrell and I did in the car where I’m driving, and he’s in the backseat, and we never got through an entire take, ever. It was supposed to be a morning shoot, and it was after lunch and we were still shooting that scene, and we still had not gotten through a single take.

Matheson: I would be running out the door to go get something that had to be rushed back to the set. A lot of times when you work on comedies, new ideas come up all the time, and you have to be ready. You never want to say no because you want to keep that enthusiasm and momentum going. And the door to the soundstage would be closed with the flashing red light, which means you’re rolling. On any other movie, you wait there for a couple of minutes and you open the door. On this movie, you’re waiting and waiting and you’re like, “Oh my God, this is an emergency, I’ve got to bring this to set.” And you’re waiting there and five minutes goes by and 10 minutes go by, and 15 minutes go by, and suddenly it’s 20 to 30 minutes. They would just roll and roll and roll, every possible version of the scene until they ran out of film. And that’s when they would open the door. So then people would say, “Well, what took you so long?” I’m like, “What took you so long?”

White: There was easily a four-hour cut.

McKay: We shot a million and a half feet of film.

White: Kodak sent over champagne. There was still a week or so of filming to go.

McKay: Late in the movie, Ferrell and Reilly come up to me and they’re just like, “Look, this movie’s going great, but we are both very tired today. Can we do one day when we just do the [script] as written?” And I went, “Guys come on. No, we’re not doing that. Look, I’ll carry you today. Don’t worry about it. You don’t have to think of anything. I’ll feed you.” And then Reilly just turned to Will and goes, “I told you he wouldn’t do it.”

Part V: “Don’t You Dare Put That in the Movie”

Step Brothers is less a film than it is a collection of sublime set pieces. Who needs an intricate narrative when you’re laughing this hard?

Hahn: It’s just absurd. To see John and Will at their most deliciously anarchic, there is something about it that just feels like you cannot believe they’re getting away with it.

Matheson: Part of my fascination with being on set was seeing these fully grown adult men embodying these children. It felt like a certain amount of one-upmanship, like, “I’m gonna jump on the bed high!” “Oh, I’m gonna jump higher!”

Ferrell: I actually had bunk beds that were constructed by my father. [It] was very impressive that my dad, who was this musician, could also build these bunk beds. That being said, they were very rickety. That first kind of ideal of wanting to have bunk beds is quickly lost when you’re in the top bunk and you have to crawl up every night.

White: When those bunk beds collapse, it’s gold. It is hands down the biggest laugh in the movie.

Reilly: Growing up, my brother played the drums and was very particular about the drum set. I’ve discovered a lot of drummers are actually very particular about their drum set. Because there’s a lot of things that can move out of position. And once you find like your perfect sweet spot where you like the drums set up and everything, you really don’t want people messing with it. But of course, like Will’s character in the movie, as soon as my brother left the house, I was drawn to it like a siren song.

Ferrell: One of my treasured keepsakes from Step Brothers [is] my pair of prosthetic testicles that I put on the drum kit.

Maginnis: I remember coming up to a producer and saying, “I think it’s gonna be hilarious and I think they’re gonna do a close-up. I want to spend a few thousand dollars and make a really good set.”

Clayton Hartley (production designer): I’m sure it was a costly venture. They needed to look real.

Maginnis: Fortunately in Hollywood there are prosthetic companies. These are the same people that I have do live casts if I need a face of an actor that looks very realistic. They basically can make any body part out of latex. Whether you’re putting hairs into a head or putting them into a sack it’s a similar process.

Ferrell: The first time I saw them, I’m like, “Yup, those’ll work great.”

Maginnis: I lost count of how many people on the crew—and I’m not gonna name any names—were like, “Do they feel real?” And how many people came up and said, “Can I cup them?”

Ferrell: I will often bring those out at dinner parties that we host.

Maginnis: He’s like, “Scott, can I keep ’em?” I’m like, “Yeah, I’m not gonna say no. I’m not even gonna ask why.”

Some of the movie’s most memorable moments were musical numbers. While riding in the family Range Rover, Derek, Alice, and their children sing an a cappella version of a Guns N’ Roses anthem. Dale and Brennan start an entertainment company called Prestige Worldwide and cut an offensive rap single. And at the climactic Catalina Wine Mixer, Sanz sings lead in an ’80s Billy Joel cover band—played by Jackshit, a country rock outfit whose lineup includes Pete Thomas of The Attractions—while Dale wails on the drums and Brennan belts out a version of Andrea Bocelli’s “Por Ti Volare.”

Hahn: It was late in the shoot when we did “Sweet Child o’ Mine.” [Adam and I] had kids the same age. Our kids decided to visit that day.

McKay: Our music supervisor on the movie, the great Hal Willner, from Saturday Night Live, he’s produced dozens of great records. We always called him the coolest person we know. When we had Kathryn Hahn and Adam Scott and the family singing in the car, he was very smart about it. I remember him telling me, “Whenever you loop music it just loses all the energy. You’ve gotta do it live.” And he was so right.

Lurie Poston (Tommy Huff): We had the Range Rover up on top of this rig in front of a green screen.

Adam Scott: I remember reading the script and being like, “Wow, this is really going to be a moment.” Either it’s going to be amazing or it’s going to be too insane and it’s not gonna be in the movie.

Hal Willner (music supervisor): We didn’t want it to be a real rocking thing but we wanted it to be good. Kathryn was a good singer. Adam actually was, too.

Adam Scott: I’m a terrible singer. And I think in order for this to really work, Derek needed to be an incredible singer. I was the only one in the car not singing live. I was lip-syncing to a guy that was standing right outside the windshield that I was locking eyes with the whole time, doing my best to lip-sync accurately. It was a thrill.

Poston: They asked me, “Can you just sing something at the end?” So I do a riff, kind of an R&B trill.

Maginnis: John comes in and he’s in hysterics because they’d done the first track of “Boats ’n Hoes.” He comes in there and he’s like, “Guys, you’re not gonna believe this, check this out!” And he just starts singing it.

McKay: We wrote it, and then I talked to the guy who made it, and I said to him on the phone, “It’s kind of like a hip-hop thing from the late ’80s, where the chorus is like, ‘boats and hoes, boats and hoes.’” And he recorded me off the phone. So the actual chorus on “Boats ’n Hoes” is me on the phone talking to the producer who made it. Crazy.

Willner: [It was] the notorious Dr. Luke*.

*In 2014, Kesha filed a lawsuit against the producer and former SNL house band guitarist, in which she said he drugged and raped her in addition to subjecting her to psychological and emotional abuse.

Sanz: I did Billy Joel on [SNL]. I’ve never really done a Billy Joel voice. It’s always just me singing being a weirdo.

Willner: However hokey these things were, they had to be great.

Sanz: I rehearsed on Lankershim [Boulevard] in the Valley in one of these old rock studios that you see in documentaries all the time. It was Hal Willner and all these real professional musicians. And I’m doing my half-assed Billy Joel.

McKay: We had the idea that [Brennan] was afraid to sing. That made us laugh. When you’re a kid, you quietly think you’re the greatest in the world—whether it’s a basketball player, singer, artist. And then you also think maybe you can’t do it at all. It’s that kind of split when you’re a kid. We set him up that he’s afraid to sing, and when he does sing he’s not that great but they act like he’s amazing.

And somehow through the story we ended up at this point where he should really sing. He should really discover his full breadth of who he is and kind of just unleash this vulnerable yet beautiful song. It must’ve been Ferrell who came up with it. I’m pretty sure he said, “Do you know this song?” And I was like, “Vaguely.” And I seem to remember him playing it and me being like, “Oh my God, this is perfect.”

Willner: He’s just singing his heart out. I think it’s kind of moving. The fact that he’s actually doing it from his heart makes it funny on another level.

Fittingly, Dale and Brennan’s musical performance was inspired by one last inspired improvisation.

McKay: There’s this final moment where Richard Jenkins is talking to Will and John after they’d just blown up the Catalina Wine Mixer. I was like, “This isn’t quite getting there.” I was like, “What’s your version of Prestige Worldwide?” He’s like, “What do you mean?” And I was like, “Why don’t you just tell a story about when you were a kid and you tried to act like a dinosaur? And eventually people told you it was stupid and you stopped doing it.” And he was like, “What do you mean?” And I was like, “Just try it.” And goes, “You just want me to make it up right now?” And I go, “Yeah, fuck it, just tell them the story. I’ll coach you from the side.” He just did it. He did a monologue. And I said, “Let’s do it one more time. You could add this.” Both of us kind of wrote it together in two takes. And then he did it again and I was like, “That was great.” And he goes, “Don’t you dare put that in the movie.”

And then I laughed and we all moved on. And I saw Richard Jenkins before the premiere, I think we had done two screenings, the first thing he said when he walked up to me, was, “How’s the movie?” And I go, “Really, really good. I think you’re gonna be happy.” And he goes, “You didn’t use that dinosaur monologue, did you?” And I go, “Hell yeah, I did!” And he’s like, “Oh my God, I’m gonna kill you.”

Adam Scott: I just saw Jenkins a month and a half ago and we talked about the dinosaur. And he was like, “I can’t believe that that’s a thing.” I think he’s just so proud of it. It’s one of my favorite parts of the movie.

McKay: Kanye West quoted the dinosaur monologue. And I saw Jenkins after that and I go, “Jenkins, fuckin’ Kanye West just quoted your dinosaur monologue.” And he’s like, “I can’t believe that’s in the movie.”

Part VI: “Unadulterated Joy”

On July 25, 2008, a week after The Dark Knight began dominating the box office, Step Brothers hit theaters. The hard-R-rated comedy, which received mixed reviews, eventually grossed $128.1 million worldwide and became a cable TV staple. Now fans are clamoring for a sequel, but true appreciation for the movie built slowly.

McKay: When it first came out, there were some people that were like, “This movie is crazy.”

White: We literally pushed it to the edge. One of the kickbacks we would get from the studio at the screenings is, “Oh my gosh, this is too crazy. This is weird.” The more anyone would say that, the more we would go, “Good, we’re on the right track. We’re doing exactly what we wanted to.”

Ferrell: We got some of the more punishing reviews that we ever had. And it might’ve kept people away.

McKay: Roger Ebert wrote this pretty bad review of it.

Roger Ebert (Chicago Sun-Times critic): Sometimes I think I am living in a nightmare. All about me, standards are collapsing, manners are evaporating, people show no respect for themselves. I am not a moralistic nut. I’m proud of the X-rated movie I once wrote. I like vulgarity if it’s funny or serves a purpose. But what is going on here?

McKay: He wrote it like he was Richard Jenkins’s [character]. And he said, [“It lowers the civility of our civilization.”] We agreed with him. That’s what the movie was meant to show! He just didn’t know we had done it intentionally. America’s kind of a fucked-up place! That’s what we’re messing with.

Dale and Brennan could get twisted into that [online] troll stuff. I could definitely see them kind of going down that road. That is kind of what happened. Those groups which were way in the distance, way in the background, kept getting closer and closer, so the person alone in their room has never been more empowered than this moment right now in history.

A.O. Scott: Of all the movies with a central theme of the male refusal of maturity, especially of that period, that is the one that went the deepest.

Willner: That was a big step for Adam. I’d known him since Saturday Night Live. Really by that point, directing, he was able to be hands-on in every way. He really knew what he wanted. It all set him up to do things like The Big Short.

Jeong: My wife and I got a chance to talk to Will at the wrap party. Most stars show up late and they leave really quickly. Will was there really early. Will was there the whole time. I told Will, “I just think McKay’s the funniest man alive.” And then Will said to me, “I’m so glad you said that.”

David Edelstein (New York magazine critic): One of the things I love about Step Brothers is watching the outtakes on the DVD, which are really hardly outtakes. There’s an extended sequence of the guys with the night-vision goggles, jumping around their room for 20 minutes. And you just think, “Oh my God, these guys had permission.” They were in a groove. When that happens on screen, you just have to treasure it.

McKay: You have a good release, everyone’s happy, and then a year later, something starts to kind of percolate. [In February 2010], Ferrell called me and he was like, “Did you read the lead story about the Saints winning the Super Bowl?” And I’m like, “No, what?” And he’s like, “Google it right now.” I called it up and it said, “After whatever years of disappointment, the Saints came into their locker room and there was silence. And then one voice yelled, ‘It’s the fuckin’ Catalina Wine Mixer.’ And all the other players yelled, ‘It’s the fuckin’ Catalina Wine Mixer.’” And I was like, “Whoa.”

Ferrell: Adam and I have discussed how there’s always been a bounce with any of these movies. ... They do those insane Turner [Broadcasting] runs, where they run it a bunch. And there’s this whole second wave.

Steenburgen: You can almost tell from the expression on someone’s face that they’re gonna mention Step Brothers. They get this stupid look.

Savage: I was going through a security gate to someone’s house in Hidden Hills, and the [guard] was like, “I traveled [500] miles to give you my seed!” And I was like, “Um, I’m sorry, what? I think I know what you’re saying and it’s very uncomfortable out of context.”

Poston: When people find out I was in Step Brothers, they freak out. “Oh, you’re that little asshole singing in the back of the car!”

McKay: I was walking down a street in New York, I think we were starting to work on The Other Guys, and I was walking down the street and I heard these two guys. One was like, “Have you seen that Step Brothers?” And the other guy was like, “I’ve seen it like five times.”

Vigman: Why do people take psychedelic drugs? They say they want to reach a higher state. I think so much of it is that we want what we must’ve felt as children. The freedom. There’s something about kids that are under the age of 6 that capture what that movie captures. When I look at my 3-year-old as she’s acting out, it nearly makes me laugh in that same way. It’s this idea of unadulterated joy.

Riggle: People always ask, “What’s your favorite movie?” I always say Step Brothers. Always. That was the most fun I ever had on a set.

Hahn: I feel like I changed as a performer, for sure, doing that movie. Just having that freedom and autonomy to really feel like you don’t just have to hit your mark and try to fit yourself into a director’s picture. What you bring to it is more valuable than anything else.

Adam Scott: It opened my eyes to this other world and I never wanted to go back. Right after the movie came out, I went and did Party Down with my friends and Parks [and Recreation]. There’s no way I would’ve been able to bring what I brought to that stuff without Step Brothers as a training ground for me.

Hahn: I am so excited to be able to show my kids this movie. One day. I’ll have to fast-forward mommy’s parts.

Adam Scott: Kathryn and her family and our kids are close friends. I showed my kids, which ended up being a mistake. It’s an incredible movie. But I’d forgotten how filthy it is. The kids couldn’t believe what they heard coming out of Kathryn’s mouth. My wife and I both were just sort of lunging for the remote.

Steenburgen: Of the many things I’ve been handed by this business, that was truly one of the ones that, from a selfish point of view, where I feel like I was given a gift. If that movie had come out and no one had gone to see it, I would still describe it that way.

Jones: I’ve always been delighted at how much Adam McKay and Will Ferrell absolutely love each other and crack each other up. And I will go on the record: Comedy is dead unless Adam McKay does another comedy.

A.O. Scott: I was in therapy some years ago. When the movie had come out, I said, “I don’t know if you’ve seen this movie Step Brothers.” And there was this hush, and then the voice from behind me kind of said, “Well, it’s a masterpiece.”

McKay: The whole nature of the movie is a lot of stories from when we were kids. Waterlogged Playboys in the woods. Shoplifting. Drama and fights with friends.

When you would hate someone, you would hate them so much. But when you were best friends, you were really best friends. The swings were so hard when you were 12. That’s where the line, “Did we just become best friends?” came from.

Interviews have been edited and condensed. Through a representative, Will Ferrell declined comment. John C. Reilly’s representatives didn’t respond to interview requests. Their quotes in this story were culled from previous interviews.