"Step Brothers" is stupid. Childish. Moronic. Simple. Juvenile. Silly. Just ridiculous.

Man, is it funny.

It falls into that weird category of films that you can't really say is good in any way, yet you would advise all your friends to see as soon as possible so that you can start repeating lines to each other over beers until you're laughing so hard, you just throw up your arms and say, "What the heck, let's see it again."

Will Ferrell and John C. Reilly star as Brennan and Dale, two adults suffering from a serious case of arrested adolescence. Both still live at home, Brennan with his mom, Nancy (Mary Steenburgen), and Dale with his dad, Robert (Richard Jenkins).

Nancy and Robert meet at a convention where Robert, a doctor, is lecturing. Soon they're married, and Brennan and Nancy move in with Dale and Robert.

One problem: Because both are spoiled, overgrown brats, Brennan and Dale take an instant dislike to each other - a violent, profane, hilarious dislike. They whisper obscene threats to each other before falling asleep at night in the room they're forced to share.

Nothing is too petty for them to fight over. Dale has a drum set he warns Brennan never to touch. You can imagine how long that lasts.

What you might not imagine is Brennan threatening to place his scrotum on the drums - or following through on the threat.

Funny? Disgusting? Who are we kidding? It's both.

This is probably a good time to point out that the wildly prolific Judd Apatow, never one to back down from a little male nudity or serious foul language, is on board as a producer.

"Step Brothers" also re-teams Ferrell and Reilly with director Adam McKay, whom they worked with on "Talladega Nights: The Ballad of Ricky Bobby." And like most of the films these fellows collaborate on, there's a nod toward a kind of sweetness.

In this case, Dale and Brennan bond over their mutual hatred of Brennan's brother, Derek (Adam Scott), a rich bully of the first order who's so controlling he assigns various vocal parts to his wife and kids so they can perform "Sweet Child O' Mine" on car rides. His wife, Alice (Kathryn Hahn), is repressed to the point that she's wildly attracted to Dale. Her pursuit of him - just as profane as anything else here - is one of the funniest things about the movie.

Then again, watching Jenkins and Steenburgen, usually upstanding types, spit out F-bombs as if they moonlight as longshoremen is pretty great, too.

Eventually, after a series of disasters, Brennan and Dale are forced to grow up. The last few scenes drag a bit as the two attempt to find their way in the adult world. But the ending eventually gets as crazy as everything else.

Certainly "Step Brothers" doesn't really have the structure of, say, a "Superbad" or "Anchorman: The Legend of Ron Burgundy." It's more like a movie as imagined and realized by a 15-year-old boy who found a copy of Hustler in his garage. If this doesn't become Howard Stern's favorite movie the moment he sees it, something is wrong with the universe.

As for the rest of us, we'll have to settle for thinking of "Step Brothers" as a movie that's gut-bustingly funny at times, even if we would never admit it.