"Step Brothers" is a movie so stupid, so primordially mindless, you can feel a lifetime's worth of higher ed and hard-won refinement leaking out of your ears as you watch it. I couldn't stop laughing at the damn thing.

The concept would fit handily on a Post-it note: Two pathetic middle-aged slackers, one still living with his single mom, the other with his single dad, suddenly become stepbrothers when their parents marry, and find themselves forced to share a bedroom. That's it.

Dale (John C. Reilly), the one vegetating at home with his father (Richard Jenkins), is 40 going on 14 — he still owns (and wears) a big Chewbacca head, and he likes to be called "Dragon." Brennan (Will Ferrell), the one living with his mother (Mary Steenburgen), is 39, and partial to Pablo Cruise T-shirts, velociraptors (the coolest dinosaur) and, when angered, teabagging. Brennan also suffers regular humiliation at the hands of his obnoxious brother Derek (Adam Scott), the white sheep of the family, a hotshot entrepreneur with a love-starved wife (Kathryn Hahn, fearlessly funny) who longs to see him smacked into line.

The movie is a delivery system for sight gags and wisecracks of a breathtaking raunchiness. They're so beyond-the-pale that I can't really quote the best of them, but Dale's remark while showing Brennan his collection of vintage skin mags ("It's like masturbating in a time machine") is perhaps suggestive of the comedic delights that lie in wait here. There's a dog-poo bit I won't go into, and a scene involving a bathroom rug and a sink for which everyone involved will be going to Hell. I curse the depraved nature that leads me to find such things funny, but what're you gonna do?

It is now law in the land of comical abomination that Judd Apatow's name be affixed to any seriously scurrilous project, and here we find it nestled among the picture's producers. "Step Brothers" is the sixth movie in just the last 12 months in which Apatow is credited as a producer and/or co-writer. What exactly he contributes as a producer isn't always clear, and it's not always a guarantee of commercial success. (It didn't salvage "Drillbit Taylor," the limp Owen Wilson comedy of a few months back). But re-teamed with Ferrell, Reilly and director Adam McKay, with all of whom he worked on the 2006 "Talladega Nights," he's in his foul element. (Ferrell and McKay wrote the script, and Reilly weighed in on the story.) True, the trademark Apatow setup — men are infantile swine — is getting frayed. It worked in "Superbad" because the developmentally arrested characters in that picture were only high school students — regressing them wasn't much of a stretch. Turning a pair of grown-ups into squalling baby-men is something else — few narrative maneuvers would seem more unpromising. And yet, for all its overbearing clamor and occasional unpleasantness, the movie is — and it shames me to say this, really it does — hilarious.

Not everything works, of course. When the 'rents order Brennan and Dale to find jobs, they set out in search of same with predictably uproarious results. But a psychotherapy subplot goes nowhere, a burial scene comes out of nowhere and a sleepwalking story thread shrivels on the screen. I'd mention that the whole tale bears no resemblance to any observable reality, but that's a given.

A lot of people would be appalled by "Step Brothers," and one feels their horror. There's no point in debating the movie's social utility — it's non-existent, and who wants to get into a pissing match?

Although ... wait a minute (spoiler): Dale and Brennan do.

Don't miss Kurt Loder's review of "The X-Files: I Want to Believe," also new in theaters this week.

Check out everything we've got on "Step Brothers."

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