A very committed cast makes 'Step Brothers' a hilariously juvenile escape
1/2
    Let's ge this out of the way right now: 'Step Brothers' is ludicrous.  It's filled with ridiculous situations, ridiculous characters, and ridiculous behavior.  Nary a minute of it is dramatically substantive or believable.  But you know what?  This is comedy, and thanks to a talented cast completely committed to the film's inherent zaniness, it's a damn funny one. 
    Will Farrell and John C. Reilly play middle-aged adolescents who must live together after their parents get married.  They're spoiled, obnoxious, and completely self-centered; a pair of walking poster-adults, as it were, for parental overindulgence.  Needless to say, they don't immediately hit it off, and their childlike quarreling escalates to a point where it strains the marriage of their respective parents, who must force them to face an adulthood they have managed to avoid for far, far too long. 
    The film reunites the two leads with director Adam McKay.  The trio formed the team behind the NASCAR spoof 'Talladega Nights'.  But unlike that outing, in which the laughs kind of ran dry a third of the way through after a hilarious opening, they manage to keep the comedy at an exquisitely juvenile level throughout the entire film, and that's as it should be.  Even though there is the requisite moment of truth for the two men and a predictable coming to terms with responsibility, the film manages to stay true it crude, immature nature the whole way through. 
    This is made possible by the relentless efforts of Farrell, Reilly, and the rest of the enthusiastic cast.  Farrell is typically adept at protraying oblivious, high-decibel obnoxiousness, but the Oscar-nominated Reilly also shows yet again that his full-hearted commitment to funny material, no matter how crude or inane, can make him a comedic force to be reckoned with.  He's a perfect foil for Farrell as well as a perfect complement to him.   Richard Jenkins and Mary Steenburgen also dive into their roles as the frustrated parents, with Jenkins of particular note as he gets a chance to flex some comedic muscle. 
    Of course, like I've said, the plot is very, very silly.  The jokes are often crude and laced with high-pitched profanity, much of which is merely for shock value.  There are pointless subplots and a few drawn out, unfunny exchanges.  It's not a film aspiring to the Woody Allen school of high comedy, so if you're expecting something intellectually engaging, you're barking up the wrong tree.   But if you're looking for a playfully idiotic indulgence with the sensibilities of Judd Apatow efforts, then Farrell and Co. have delivered just the thing for you.

Oh, and don't immediately leave when the credits start rolling.  A few moments into the credits, there's one of the most ridiculously hilarious prologue scenes I've seen in quite some time.  I literally laughed throughout its entire duration.  That'll probably reveal something about my personal sense of humor, for better or for worse.