There are so many things for which we should thank Judd Apatow in this joyous time of year. He made it through the fire of failed-but-brilliant television comedy like Freaks and Geeks and Undeclared to become film comedy’s current grandmaster with The 40-Year-Old Virgin and Knocked Up. He has developed a talented company of writers and actors that has resulted in the likes of Superbad. But now, with the arrival of Walk Hard: The Dewey Cox Story – co-written by Apatow and frequent collaborator Jake Kasdan – we may have the best reason yet to thank him: He has made it impossible for anyone ever again to pitch a musical biopic with a straight face.

Now there appear to be plenty of viewers who groove to the glossy, high-minded stylings of big-screen celebrity tell-alls like Ray and Walk the Line. But there are others among us who can’t quite grasp the love heaped on these movies year after year. With an almost comforting predictability, they tweak the specifics in boilerplate scripts covering hardscrabble youth, improbable rise to fame and struggles with various vices.

Walk Hard tears into the clichés of this genre with hilarious, near-relentless ferocity. The tale takes us back to the 1940s Alabama childhood of young Dewey Cox, when the accidental death of his brother earns him the enmity of his father (Raymond J. Barry) and a drive to make something of himself. But even as the grown-up Dewey (John C. Reilly) begins to find success as a singer and songwriter, he finds it hard to escape his traumatic past. Can he overcome his first wife’s (Kristen Wiig) repeated insistence that he’ll never make it? Will he succumb to the tempting drugs provided by his drummer (Tim Meadows)? And will he overcome his troubles in time to save his second marriage to his backup singer Darlene (Jenna Fischer)?

Literally from the first minute to the final post-credits payoff, Kasdan and Apatow mercilessly skewer the conventions of the biopic. Leaden foreshadowing takes a beating as Dewey’s doomed brother begins his last day exclaiming, “Nothing terrible could possibly happen today!” Cradle-to-grave performances become fodder for Reilly’s first appearance as “14-year-old” Dewey. There’s the familiar recording studio sequence, in which everybody instantly realizes they’re in the presence of music history in the making. The downward spiral of Dewey’s stair-step addiction climb from marijuana to cocaine to pills becomes a politically incorrect celebration of the appeal of getting high. And the “harrowing” cold turkey detox sequence? Pricelessly overwrought.

But as much as it’s a musical parody, Walk Hard is, in fact, musical. The title song, co-written by Marshall Crenshaw, simply evokes vintage Johnny Cash rockabilly. But when the songs do aim for comedy, they’re uniformly brilliant. The already infamous double-entendre-laden “Let’s Duet” only sets the table for a Dylan-flavored protest song in support of little people, a crazy didgeridoo-flavored symphony from Dewey’s crazy Brian Wilson period, and an oh-so-literal career summation.

When you’re dealing with a satirical comedy in the Airplane! tradition, you can’t expect every joke to hit the bullseye. Apatow and Kasdan over-use a gag with record industry execs as Hassidic Jews, and some of the more outrageous bits succeed at being outrageous without necessarily being outrageously funny. But Walk Hard remains laser-focused on deflating the self-importance of trite stories about tortured artists.

WALK HARD: THE DEWEY COX STORY ( 3 ½ ) Directed by Jake Kasdan. • Starring John C. Reilly, Jenna Fischer and Tim Meadows. • R, 98 min. • At the Century Cinemas Del Monte Center, Maya Cinemas, Northridge Cinemas.