Will Ferrell’s frequent roles as overgrown man-children have earned some criticism over the years, but even the toughest critics are likely to be won over by Step Brothers, Ferrell’s latest effort with director Adam McKay (Anchorman, Talladega Nights) and one of his funniest comedies in years. With John C. Reilly upgraded from Talladega’s second banana to true co-star status, he and Ferrell run wild through the movie’s basic plot, creating a satisfyingly simple and absurd comedy.

Brennan (Ferrell) and Dale (Reilly) are horrified when their single parents (Mary Steenburgen and Richard Jenkins) marry, forcing the two to share a room and fight over everything possible. The brotherhood starts off rough, with Brennan rubbing his genitals on Dale’s beloved drum set and eventually attempting to bury Dale alive. But soon a more important enemy arrives: Brennan’s older brother Derek (Adam Scott), a helicopter rental executive with pomaded hair and bullying tendencies left over from childhood, when he forever traumatized Brennan. Dale punches Derek, Brennan is in awe, and a friendship is born.

Step Brothers doesn’t have a plot so much as it has a series of funny bits, which occur based on whether or not Dale and Brennan are friends at the time. There’s the epic fight sequence that leads to one of them brandishing a bicycle as a weapon, and then there’s the series of job interviews the two conduct while wearing tuxedos. That’s followed by a schoolyard battle royale in which the brothers are beaten up by 11-year-olds, and finally the all-important Catalina Wine Mixer, with entertainment from Uptown Girl, California’s premier 1980s Billy Joel cover band. There’s a side plot about Mom and Dad’s plan to retire and force Dale and Brennan to get jobs, but that’s mostly an opportunity to set up some gags that take place in the outside world. McKay, Ferrell and Reilly, who co-wrote the script, seem to be aiming for a character-driven comedy with zero character development, more like a “Saturday Night Live” sketch than a movie. The miracle is that the basic concept actually carries Step Brothers through its consistently hilarious running time.

Reilly and Ferrell are an appealing duo, but they’re generous with the laughs as well, handing off meaty scenes to Jenkins, Scott, and Kathryn Hahn as Derek’s sexually frustrated wife with the hots for Dale. McKay directs the whole thing with a zippy pace, so that by the time you reach that Catalina Wine Mixer, you don’t notice that pretty much no plot has appeared. Enjoying Step Brothers may require regressing to an adolescent sense of humor, but why resist? There’s something in all of us that wants to laugh when two grown men don matching Chewbacca masks in their treehouse. After absorbing the bleak fireworks of The Dark Knight, we all could use a few hours with Ferrell and Reilly as they unleash their aggressive, childish ids.