Everybody’s got that friend. He can’t get through a sentence without a few f-bombs and would rather chat about your or your wife’s breasts – right in front of you -- than about the babbling newborn twin babies nearby. He doesn’t know how high is a little too high to be playfully tossing a little girl in the air. He doesn’t know how to talk to children, or about children, or even about growing up. Because he is a child.

“You see that look of innocence in that little girl's eyes and you say, ‘I need to push her into the stairs. I need to quiet that innocence,’” Ryan Reynolds laughs, after shooting a scene where he does just that.

That’s Reynolds’ Mitch in “The Change-Up,” forthcoming from “Wedding Crashers” director David Dobkin and “The Hangover” writers Jon Lucas and Scott Moore. The “Green Lantern” actor performs opposite of Jason Bateman’s Dave, who plays into somewhat familiar territory as a family man holding down the domestic fort with wife Jamie (Leslie Mann). Mitch is a blonde-streaked womanizer and aspiring actor, still living in a man-cave covered with band posters and college tchotchkes, and best-friend-since-high-school Dave has a straight-laced j-o-b (and law associates with what’s described as “dream girl” Olivie Wilde, as Sabrina).

Now imagine they magically switch, switch bodies, and go through what Dobkin describes as a “hall pass” conversation about men, marriage and fidelity (and what you’d have tattooed onto your buddies body while he’s not “looking”).

Does it sound a little heady? Add in the movie’s hard-R rating. This is no “Vice-Versa.”

[More after the jump...]

“I mean, they piss in the fountain. How f*cking serious do you think we’re taking the body switching?” Dobkin concedes, describing how “the switch” is done.

Reynolds and Bateman get about one-third of the movie in their own skin before the magic occurs, and there’s full-color Bateman with a bachelor palate and Reynolds facing the very real possibility of seeing someone other than his “wife” naked.

On set in Atlanta, the two actors convinced at least a few of us journalists that their “Freaky Friday” moments may be untamably filthy.

“There [have] been a few PG and PG-13 versions of the body-swapping movie. We've all seen them and they've been great,” Bateman says. “It's a great, simple, easily relatable concept made fresh by throwing the whole fish out of water conceit into deeper and rougher waters… And they're really done a great job by putting us in as risqué and gratuitous situations as possible, but having the characters be charmingly underwater. Most of the time they're not driving these unseemly situations, they're a victim of them.”

In other words – as indicated by the red-band trailer – that puts Batemen accidentally cradling his naked junk in front of a full audience and talking down to a second-grader. That’s the tattoo parlor and a single-man’s life for Dave. And according to the actors, the script had the room to take it as far as they wanted to go, and the chemistry was on from the get-go.

“I wanted to work with Jason,” Reynold said, recalling he’d read the “Change-Up” script as he was shooting ultra-serious “Buried.” “I remember reading it and sitting in bed and crying laughing. [I thought] ‘I've got to do this somehow, or just get it on a loop in my house if someone else does it?’ I really, really was attracted to it, and it came through on all levels. You get scared if you're working on a movie that you have a really good time on, because you think, ‘How can this be good if I'm having so much fun.’ It's been that from day one.”

The unorthodox pairing was part of the scheme of building a “done” comedy concept from the ground up.

“I’m always looking when I cast people to do something that I think they haven’t done… Jason ends up being that guy for most of the movie, which is really kind of awesome and freaky and weird,” Dobkin says.

“The Hangover had this thing where it could have been Will Ferrell, Vince Vaughn and Steve Carell. It could have been the straight guy, the clown and the scoundrel. Or it could have been three guys you didn't know that well. And part of its success, I think, came from the fact that you didn't quite know who they were, and these guys might kill a hobo in this movie,” Lucas says. “Will Ferrell is never going to kill a hobo. He's a great guy, but he's got another movie to do after this one, and he'll never go that far.

“This is great because… Jason Bateman doesn't get the call very often to do dirty material. He's always the nice dad who's struggling a little bit. And he gets to do that and then he's just an animal.”

And from some of the scenes the filmmakers previewed for us, dirty suits him, because it’s based on a premise spawned from reality. Lucas recalled a monthly dinner he has with a mix of pals; some men like himself are married and some are very, very single. “The conversations we’d have – it’s like the people they pull out of the jungle who don’t understand how electricity works. I’m asking questions that are so dumb about being single like, ‘What do you say, how do you do it? That sounds so crazy!’ and they’re like, ‘You’re married, do you have sex like once a day? Or twice a day?” and I’m like “Are you out of your f*cking mind?!’ Some of that stuff got into the script. And that’s some of the funniest stuff.”

Dobkin gives it his own spin on man’s big dumb problem, and how movies like “The Change-Up” may scratch that itch.

“I remember seeing Blake Edwards' “10” when I was very young… And I wondered how I would feel as an adult with kids watching that movie. Julie Andrews is his girlfriend in the movie and she's like America's sweetheart. The whole thing is he goes chasing this girl in a mid-life crisis and it's fascinating to me because men can be retarded like that. They just don't f*cking grow up when it comes to women, no matter what happens,” he says. “It's a question of men and I think ‘The Hangover’ and ‘Wedding Crashers’ and a lot of these movies right now are about good dudes who are behaving badly and really need to be taught a lesson. And for some reason it's really funny.”

The “sweetheart” in “Change-Up” is Mann, who’s made her mark in Judd Apatow films and goes toe-to-toe with all the other actors and acts as the ground wire to the excessive activity of Dave and Mitch. Like when Mitch can’t help but comment on her butt.

“I think it's pretty clear early on that Mitch thinks she's a hot little number,” Reynolds says.

“He doesn't have an edit button,” Bateman adds. “We all have one of those in our lives.”

“We all have a guy like that.”