Rainn Wilson has the title role in The Rocker, drumming his way to stardom later in life in his nephew’s band.

Twentieth Century Fox / George Kraychyk

At one point late in the offbeat comedy The Rocker, drummer Robert Fishman declares, “It is never too late to rock!”

That’s the theme of this engaging film in which the middle-aged “Fish” grabs at a second chance to do what he loves more than anything — pound the drums on stage in a hot rock ’n’ roll band.

Played by chunky, round-faced Rainn Wilson of TV’s The Office, Fish is hardly the typical movie leading man. He looks a little like a grownup version of the Chucky doll in all those horror movies. But Wilson is just what this very untypical underdog story needs to capture its unusual qualities and make it very special. When things finally begin going Fish’s way, we cheer him and the most unlikely set of circumstances that brought him to that point. It’s rock ’n’ roll. It’s over the top. And it’s uplifting.

But things get off to a rocky start for Fish in director Peter Cattaneo’s fresh, offbeat film. Cattaneo’s biggest previous success was The Full Monty, so anything’s possible. The Rocker opens in 1986 when, just as national success seems to be within Fish’s reach with his three band mates who make up Vesuvius, he’s kicked out of the group at the request of the record label that wants to sign the other three guys. This treachery doesn’t go over well. In a very funny sequence Fish assaults the van in which his three former buddies are speeding away.

Flash to 20 years later. Fish is in a dead-end job at a big corporation, still fuming about being dumped by Vesuvius. Whenever the band’s name comes up, he goes into a violent rage. This is why, before long, he’s suddenly unemployed and living in his sister’s attic in Cleveland.

But a glimmer of hope emerges when the drummer in his nephew’s band, A.D.D., runs into a little legal trouble and is no longer able to play the band’s first big gig at the high school’s senior prom. Nephew Matt (Josh Gad) implores Fish to sit in for the night and rescue the event for them. Fish is reluctant but, of course, is soon banging with the drumsticks. But memories of his past catch up with Fish on stage as he takes over the stage with his overly exuberant, spotlight playing, leaving his band mates in A.D.D. as well as the prom crowd aghast at his antics.

It looks like disaster for Fish again. He’s almost kicked out of his nephew’s band, until his unlikely accidental appearance on an Internet site, practicing naked on the drums, turns him into a national sensation. In a nanosecond he has become famous as “The Naked Drummer.” And before you can say “heavy metal,” there are bookings for A.D.D., with Fish once more heading for stardom (or notoriety) once he straightens out lead singer and songwriter Curtis (Teddy Geiger), whose tunes have a deadly, world-weary tone.

Fish is the sparkplug that ignites A.D.D.’s playing in concerts and Wilson is endearing in his wide-eye enthusiasm as the charismatic Pied Piper who is Robert Fishman. Yet once Fish’s inner animal is unleashed, it’s difficult to put it back in its cage. A national tour, which the parents of his teenage band mates have agreed to only reluctantly, is headed for disaster thanks to Fish’s unbridled determination to party like mad.

This leads guitar player Amelia (Emma Stone) to enlist her mother, Kim (Christina Applegate), to go on the road behind the scenes with them and give the band an even-keeled Partridge Family touch. Applegate, all grown up and no longer the sassy and brassy Lolita figure from her stint on TV’s long-running Married … With Children, is a quick-witted, competent and caring mother figure here … and maybe more, it’s hinted.

The comedy in the script by Maya Forbes and Wallace Wolodarsky is not as wacky and wild as Fish’s playing. It sneaks up on you. But once it does, the laughs come easily and the music, with songs by the likes of Peter Gabriel as well as original material by Chad Fischner, are punchy and hummable which will make for a soundtrack album that’s almost as good as the movie itself.

****The Rocker

Starring: Rainn Wilson, Christina Applegate, Teddy Geiger, Josh Gad, Emma Stone.

Rated: PG-13, contains nudity, profanity, adult themes.

mjanuson@projo.com