Ferrell plays Brennan, a 39 year-old man-child. John C. Reilly plays Dale, a 40 year-old man-child. Their lives change when Brennan’s mother Nancy (Mary Steenburgen) marries Dale’s father Robert (Richard Jenkins). Since both men still live with their respective parents, the marriage brings everyone together under the same roof. Like child step siblings, Brennan and Dale are initially suspicious of one another. Further complicating things is that Dale refuses to give up his “drum office,” so he and Brennan have to share a bedroom.

The humor in the early part of the film is centered around the fact that these two guys act like children and hate each other. Brennan lounges around in his Star Wars pajamas and threatens to punch Dale in the face while he sleeps. Dale walks around in his tighty-whiteys and gets his step brother going by insinuating that he, like his father, intends to sleep with Nancy. Eventually the parents get fed up with the bickering, so they give the boys 30 days to find jobs and move out. Fortunately, the two discover some common ground in this time, including a mutual hatred for Brennan’s showboating brother Derek (Adam Scott).

Step Brothers is one of those movies that leaves me teetering on the fence. Parts of it are incredibly funny. Once again using an improv-heavy style, Ferrell and his collaborators (co-writer/director Adam McKay and producer Judd Apatow) provide the basis for some moments of uproarious absurdism. There’s a hysterical running joke about Brennan and Dale destructively sleepwalking, and a scene involving dog dirt that is so old it’s turned white is as gross as it is belly laugh-inducing. I also laughed at some of the goofball concepts, such as the two trying to make homemade bunk bed, or the outrageous scene in which Derek’s wife (Kathryn Hahn) tries to seduce Dale in a public restroom.

Despite some undeniably funny moments, Step Brothers has a few problems that prevent it from reaching the comic heights of, say, Anchorman. For starters, the whole “man-child” thing has been done a lot in movies. We’ve seen characters like this before, played by everyone from Adam Sandler and David Spade to Steve Carell and Seth Rogen. It’s not exactly a fresh concept; how many times can a grown man with a bedroom full of toys inspire you to giggle? It only makes matters worse that there are two man-children in this movie. Brennan and Dale are exactly alike in every way, so we get two repetitive characters for the price of one.

And speaking of repetition, the film essentially trots out the same jokes again and again. Dale is obsessive about his drum kit. Brennan has repressed hostility. The boys run out to their tree house whenever they are in trouble with their parents. The effect of this humor wears off after a while. So does the vulgarity. Step Brothers pushes the boundaries of R-rated humor. The main characters all speak to each other in streams of vulgarity-filled insults. Any time someone can make a reference to a body part, a bodily function, or an aberrant sex act, they do. And their language is peppered with the F-word, and the MF-word, and other, similar things. I actually like this kind of humor. Always have. In this case, it’s funny for a while, until you realize that there’s basically no plot here (just a one-note concept) and all the raunchiness is being used to camouflage that fact. When I was a kid, my father used to take me to R-rated comedies, unbeknownst to my mother. He would always remind me, though, that profanity is funny only when it emphasizes a comic idea. In Step Brothers, the profanity is the comic idea.

In spite of these issues, I was still mostly going with the picture. What ultimately makes it a “rent it” movie instead of a “run out and see it” movie is the final half hour. The last third of the film takes place at a posh wine tasting event, organized by Brennan to impress his family. It is here that Step Brothers comes crashing to a halt. This section is flimsy because it’s clearly just a set-up to resolve what little story there is. It also provides not a single substantial laugh. You can feel the movie going through the paces, trying to find a way to wind everything up. It’s a clunker.

If, like me, you are a big fan of Will Ferrell, you will want to see Step Brothers anyway, just for the occasional jokes that do work. That said, unlike Old School or Anchorman, this isn’t one that you’ll want to watch over and over or quote back and forth with your friends.

( 1/2 out of four)

Step Brothers is rated R for crude and sexual content, and pervasive language. The running time is 1 hour and 33 minutes.

To learn more about this film, check out AskMen.com: Step Brothers