Twenty years later, Fish is unemployed and still resentful of the betrayal. He gets a shot at redemption when his teenage nephew Matt (Josh Gad from 21) asks for help: his band A.D.D. is scheduled to play the school prom, but their drummer has had to drop out. Fish reluctantly agrees and ends up becoming a full-fledged member of the group, which also includes insecure bass player Amelia (Superbad's Emma Stone) and brooding guitarist/singer Curtis (Teddy Geiger). During one of their practice sessions, Fish drums in the nude and footage of it ends up on YouTube, creating an internet sensation. Immediately afterward, a smarmy record company exec (Jason Sudeikis) comes calling, offering A.D.D. a contract, a tour, and eventually a spot opening up for - you guessed it - Vesuvius. Curtis's mother Kim (Christina Applegate) goes along on the tour to make sure that the ever-rockin' Fish doesn't corrupt the adolescents.

On the surface, The Rocker appears to be yet another man-child comedy about a guy who refuses to grow up, and in a way, that is part of the story. Fish dives right back into the rock-and-roll lifestyle as soon as he steps behind a drum kit, seemingly oblivious to the fact that his bandmates are mere teenagers. He screams out tour bus windows, trashes hotel rooms, gets drunk and tries to pick up groupies, and even rides a tricycle into a swimming pool. At all times, he imagines himself as something of a heavy metal Yoda, trying to impart the hard-rocking ethic to his shy, awkward companions.

Such scenes do provide many of the film's laughs, but what I liked most about The Rocker is that it transcends the man-child comedy trap. Unlike the disappointing Step Brothers, which presented doofus behavior for its own sake, this picture roots its character's doofus-ness in an honest-to-goodness story. Fish isn't just a guy who refused to grow up; he's a guy who was robbed of his opportunity to be young and wild, so he runs with it when it becomes available two decades later. At all times, we believe that he really is a wounded guy, ever bitter about being left behind by Vesuvius. It's also great that he gives Matt, Curtis, and Amelia good advice just as often as not. Although he encourages them to be more wild and uninhibited like any rock star worth his/her salt should be, he also supports them through any crises they may have and nurtures their creativity.

Fish is a 3-dimensional character, wonderfully brought to life by Rainn Wilson. I first figured out who Wilson was when I started watching "The Office." When I later looked him up on IMDB, I was stunned to realize that I'd already seen him in literally dozens of movies. Dwight Schrute was his breakout role, but a glance at his credits reveals an actor of uncommon versatility and range. There can be a trap when an actor embodies a character as popular and singular as Dwight: when the actor takes other roles, he/she can sometimes fall into the rut of playing variations on that character. Wilson doesn't do that. Watching The Rocker, you never once think of the anal-retentive cubicle drone. Instead, you see a totally different guy - one who is loose and freewheeling and a whole other kind of crazy.

Wilson is fantastic here, and so is the supporting cast, which also includes Will Arnett as the leader of Vesuvius. The story's basic concept is perhaps a little on the far-fetched side, yet the actors sell it. Director Peter Cataneo (The Full Monty) also really knows how to mix moments of wacky humor with other moments that are more heartfelt and human. Like any good filmmaker, he seems to understand that the comedy is funnier when rooted in something real. Too many comedies of this kind are worried only about the funny. The Rocker wants to make you care while you laugh.

There's nothing particularly groundbreaking here. You can get a general sense of where the story is going well before it gets there, and it's not hard to figure out what the characters will have learned by the end (although there is a delightfully topical scene with Vesuvius in the final minutes that I didn't see coming). Even so, the movie has a smart, sharp screenplay from Maya Forbes and Wallace Wolodarsky that is filled with witty lines of dialogue and clever scenarios.

I had a really good time watching The Rocker. I laughed, I tapped my foot to the music, and I reveled in the extraordinary Rainn Wilson, who once again takes an over-the-top character and somehow makes him believable. Personally, I'd play Guitar Hero with this guy any day.

( out of four)

The Rocker is rated PG-13 for drug and sexual references, nudity and language. The running time is 1 hour and 42 minutes.