Recent disasters such as Date Movie and Epic Movie strongly suggested that parody is dead. Perhaps devolution’s to blame: After all, it’s been a long time since the heydays of Mel Brooks and Zucker-Abrahams-Zucker. Maybe Mother Nature decided that this particular talent gene was so increasingly underused, humans really didn’t need it anymore.

But here’s Walk Hard: The Dewey Cox Story. Who knew that Judd Apatow, the newly anointed master of sex comedies, also spoke jive? Apatow co-wrote Walk Hard with director Jake Kasdan (who negotiated some fine, if little-seen, satire of his own with this year’s The TV Set), with John C. Reilly starring as Cox. For years Reilly was best known as “that guy”—he spent the early part of his career doing character work in dramas until he got the chance to upstage Will Ferrell in Talladega Nights: The Ballad of Ricky Bobby. Casting Reilly as a comedic lead in a hugely anticipated holiday opener may have seemed like a risk, but doubters need only glance at Reilly’s goofy mug on the film’s poster to get that this was an inspired choice.

Walk Hard is a sendup of the musician biopic in general, but mostly it sews together the scenes and storylines of Ray and Walk the Line. It begins as Cox is about to give his final performance, with a young producer trying to rush the singer, whom he finds facing a wall with arm outstretched and head down. “Give him a minute, son,” says Cox’s bandmate, Sam (Tim Meadows). “Dewey Cox needs to think about his entire life before he plays.” Indeed, there’s a lot to think about: Young Dewey (Conner Rayburn) wasn’t as gifted as his brother when it came to music but decided to dedicate his life to it anyway after accidentally slicing little Nate (Chip Hormess) in half in 1946. He later causes a riot at his Alabama high school with a gentle pop song, “Take My Hand.” (“You know whose got hands?” a preacher yells. “The devil!”) Eventually, Dewey becomes a janitor at an all-black nightclub and gets his break when the headliner (The Office’s Craig Robinson) is sick.

One performance of “(Mama) You Got to Love Your Negro Man” later, and Dewey is hip-thrusting his way to stardom, complete with the attendant drugs, sex, and desperate late-stage career reinventions. This life might have been tough for Dewey—at one point, he cries, “Goddammit, this is a dark fuckin’ period!” while jackhammering a blonde—but Walk Hard delivers a pretty steady stream of fine moments. The humor gets naughty, but in general it’s more Simpsons than Superbad. Anyone who was rightfully appalled at August Rush, the recent film about a musical prodigy, for instance, will laugh their asses off when Dewey becomes a blues virtuoso the first time he picks up a guitar, with Sam Jackson’s Black Snake Moan voice coming out of Dewey’s baby face.

With a great script and South Park-­worthy songs supporting him—try to get “Let’s Duet,” a June & Johnny spoof with Jenna Fischer, out of your head—Reilly could have gone through the motions and still gotten laughs. But he’s brilliant in Cox’s various periods, from slick-haired teenybopper (Reilly plays a 14-year-old, an apparent nod to Kevin Spacey’s misguided self-casting in Beyond the Sea) to Cash-esque country star to curly-haired, logorrheic Bob Dylan (easily outdoing Cate Blanchett’s ballyhooed I’m Not There turn). The supporting cast deftly handles the silliness as well, especially Raymond J. Barry as Cox’s dad and Kristen Wiig as his harried first wife, and, in one of the movie’s best scenes, cameos by Jack Black, Paul Rudd, Jason Schwartzman, and Justin Long as…the Beatles. Turns out that parody wasn’t dead after all. It just went through a dark fuckin’ period.