Step Brothers is pretty much a one-joke film — Ferrell and Reilly as 40-year-olds but with the mentality and maturity of 10-year-olds. They still live at home with their respective single parents. They don't work. And that's the film, in a nutshell. But surprisingly, it works — thanks mainly to the chemistry of the two leads.
Ferrell is Brennan Huff, who lives with his dad (Jenkins). Reilly is Dale Doback, who lives with his mum (Steenburgen). When their parents meet, fall in love and marry, the two "boys" are shattered — they are forced to live in the same house (even having to share a bedroom), and become step-brothers. But this ain't The Brady Bunch. For a start, there's not as many kids. And the melding of the two families does not go as smoothly as in that sickly-sweet 70s sitcom. Dale and Brennan constantly fight and bicker, driving their parents mad. Until a mutual loathing for Brennan's successful younger brother, Derek (Scott) unites them.
The last time Ferrell and Reilly were together was in the so-so Tallageda Nights. This is a far better film, albeit one with a very slim premise. The jokes, for the most part, do hit their target, and the performances of the two leads are great. I've never been a big fan of Ferrell's — Anchorman and Stranger Than Fiction are the only two films of his that I've really liked — but in Step Brothers he's firing on all cylinders, ably assisted by Reilly, Jenkins and Steenburgen. The plot is paper-thin, but there are just enough laughs to sustain the runtime.