Last week, it was director Jason Reitman (son of Ivan) opening his movie Juno. This week, it’s Jake Kasdan (son of Lawrence) opening Walk Hard: The Dewey Cox Story. When did Hollywood become so entirely Coppolaized? I half expect to check out the coming attractions and discover offerings by Alex Scorcese, Little Tommy Tarantino, and the Scott cousins.

Happily, while Walk Hard is no Juno, neither is it anything likely to inspire the passage of anti-nepotism legislation. The story begins, like all tales of transcendent musical genius, with the death of a brother. Rural piano prodigy Nate Cox is practicing a concerto when his six-year-old sibling Dewey lures him out to play. “Today’s going to be the best day ever,” Dewey exults. “Yeah, ain’t nothing horrible going to happen today,” adds Nate. The two engage in typical boyish hijinks such as welding and rattlesnake-handling, before Nate has an idea: “C’mon Dewey. There’s nothing wrong with a little machete fighting.” (The outcome, though tragic, is rendered less so in hindsight when we learn that, had he lived, angelic Nate would have grown up to be a foul-mouthed butterball played by Jonah Hill.)

Dewey, too, suffers his share of hardship when he loses his sense of smell, but he doesn’t allow this disability to hold him back. He gets his first taste of fame at age 14 (though already bearing a suspicious resemblance to 42-year-old John C. Reilly), when his tender pop ditty “Take My Hand” inspires lasciviousness and fisticuffs at the local sock hop. From there, he’s on his way: He records hit songs, beginning with the Cashesque anthem of perseverance “Walk Hard”; acquires a wife and several kids; meets his June Cartery muse (Jenna Fischer); experiments with marijuana even after being warned that it’s harmless, inexpensive, and non-habit-forming; and tears the sinks out of countless bathroom walls.

The conceit for the film is so slender that one keeps expecting it to break, but Kasdan and co-writer Judd Apatow keep it zipping along nicely, with drive-bys of Elvis, Bob Dylan (Reilly’s impression puts Cate Blanchett to shame), “The Partridge Family,” Charles Manson (“His music is terrible,” Dewey is informed, “but he’s a really nice guy”), ’70s musical-variety shows, and the Beatles. (Paul Rudd’s cameo as John Lennon is deliriously inspired.)

For years, it seemed as though no one else in American film could manage Will Ferrell’s winning style of irony-free humor, his ability to be the joke without constantly reminding us that he’s in on the joke. But Reilly seems to have inherited the comic manner of his Talladega Nights costar, and underplays his idiocy nicely, with nary a wink throughout. As a teenybopper fan of Dewey’s effuses early in the movie, “He walks so hard.”

--Christopher Orr