Box Office Mojo lists Judd Apatow as a producer on 27 movies. 23 of the 27 appear on the same page in a chart ranking Apatow’s worldwide box office totals. The lowest-grossing film, Apatow’s biggest flop ever from an international perspective, is 2007’s Walk Hard: The Dewey Cox Story. Despite a terrific cast, incredible jokes, and the eminently mockable subject of the musical biopic genre, Walk Hard earned just $20.6 million; significantly less than Apatow misfires like Drillbit Taylor and Year One.

The words of the film’s title song were sadly prophetic; Dewey Cox was scorned and slandered, and had to struggle everyday his whole life through. But ten years to the day of its theatrical debut, its time to perform a different sort of accounting and acknowledge that Walk Hard is, if not the best Hollywood comedy of the 21st century, then certainly the most underrated.

It’s a spoof of the formulaic prestige biopics of the mid-2000s, including Ray and Walk the Line. These films rehashed the same story beats about great but troubled artists over and over: Trauma-filled childhoods, substance-abused-filled adulthoods, early successes, broken marriages, midlife comebacks. The repetition made for some forgettable films, and some extremely fertile ground for satire.

Enter Dewey Cox and Walk Hard, produced and co-written by Apatow with its director, Jake Kasdan. It apes several of these movies, particularly Walk the Line, in imagining the life and times of a musician played by John C. Reilly. Like the Johnny Cash of Walk the Line, Reilly’s Dewey Cox flashes back to his entire life story backstage at an important concert; like Johnny, Dewey is haunted by the death of his brother. Only in this case, the elder Cox is stricken with a particularly bad case of being cut in half.

The death of Nate Cox is a funny scene, and a bit of a mission statement for Walk Hard: For 96 minutes, Kasdan and Apatow hack away at a thicket of biopic clichés. There’s a shrewish, unsupportive wife (Kristen Wiig) who insists her talented husband will never amount to anything (even, in this case, after he’s already a huge success); a sensual mistress and collaborator torn between desire and decorum (Jenna Fischer); and a disapproving father (Raymond J. Barry) who is never satisfied by his pathetic waste of a son (and who never lets him forget that the “wrong kid died!”). There’s also Reilly trying, as so many biopic stars do, to pass himself off as a teenager. (Reilly, age 42, is introduced as Dewey at age 14.)

In one particularly hilarious scene, Dewey travels to India on a spiritual quest, where he encounters the Beatles, played with very little attempted accuracy by Jack Black, Paul Rudd, Justin Long, and Jason Schwartzman. The sequence perfectly deflates several of the most hackneyed biopic tropes all at once: Stunt casting, improbable moments of inspiration, and laughable shorthand dialogue used to quickly explain who an important figure of history is to the audience (“What do you think, George Harrison of the Beatles?”):

The lacerating screenplay is good, but the key to Walk Hard’s success is Reilly. The surreal comedy subgenre known as the spoof is associated with non-stop jokes and absurd digressions of plot and character. But like all the best spoofs (Airplane!, The Naked Gun), Walk Hard has a protagonist you genuinely care about; a good-hearted idiot to root for amidst all the silliness. Dewey Cox may be a womanizing, pill-popping, brother-murdering egomaniac, but he’s also a broken soul searching for peace and acceptance (and his sense of smell; he lost his sense of smell when Nate died). Reilly brings a sweetness and innocence that keeps Dewey likable even in the character’s “ dark f—ing period,” as he puts it. There’s no guile to Dewey, whether he’s accidentally (or not so accidentally) committing bigamy or trying marijuana for the first time.

(Walk Hard’s drug scenes are probably the film’s most famous moment, but there’s a button on the joke that few notice. Throughout the movie, Dewey samples every single drug Sam puts in front of him, except the last one. Finally, Dewey learned his lesson. And it is at this point that he promptly dies. Basically, the one time Dewey says no to drugs, it kills him.)

Reilly is also surprisingly convincing during the film’s musical numbers, which come in a variety of genres and styles as Dewey’s career mutates to match his times. (“Take My Hand” is innocent pop, “Royal Jelly” is Bob Dylan folk, “Beautiful Ride” concludes Cox’s tale with an inspirational ballad.) Some lucky fans even got to watch Reilly perform the film’s songs live (in character!) around the film’s release as part of a “Cox Across America” tour designed to promote the film. The best track is the innuendo-laden “Let’s Duet.”

I wouldn’t necessarily expect an R-rated comedy starring a perennial second banana to break box-office records, but the degree to which Walk Hard flopped baffles me to this day. You could blame it on the fact that spoofs, a Hollywood staple of the ’80s and ’90s, had fallen out of favor with audiences by the mid-2000s, and to some extent they had. Still, Walk Hard earned less in U.S. theaters than three of the four spoofs released in the 2000s by Jason Friedberg and Aaron Seltzer, even though their comedies have all the humor of a endoscopy performed without anesthesia. Clearly there was an audience left for spoofs. They just didn’t show up to admire John C. Reilly’s Cox.

Perhaps Walk Hard was simply too ahead of its time. It was released just two years after Walk the Line, while interest in the genre was high. By the time the Zuckers made Airplane!, the Airport franchise was a decade old and disaster movies had been driven into the ground. The same year Walk Hard was released, Marion Cotillard won the Academy Award for Best Actress playing Edith Piaf in La Vie en Rose. Audiences need to be tired of something before they show up to mock it; they may not have been tired of the musical biopic.

Hollywood certainly wasn’t tired of it; they’ve continued to release music biopics in steady numbers over the last decade, including films about James Brown, Hank Williams, Frankie Valli, Jimi Hendrix, and Miles Davis. A few of these movies mixed up the formula, but nearly all had at least one or two scenes previously skewered in Walk Hard. With each new film, and each new great artist who succumbs to temptation (but not the Temptations), the film’s legend grows. Ten years later, it’s funnier than ever.

Looking back at that list of Judd Apatow’s box office grosses suggests another possible theory. As a producer, Apatow only has two wide-releases that bombed harder than Walk Hard in the U.S. The absolute bottom of the barrel, with less than a third of Walk Hard’s already measly domestic earnings, is Popstar: Never Stop Never Stopping, the Lonely Island’s very funny satire of modern pop stardom. Popstar is one of the few recent movies that can challenge Walk Hard for the title of the funniest film of the 21st century. And it made $30 million less in theaters than Meet the Spartans. Maybe music fans take themselves too seriously to take a joke? For some audiences, the spoof is a hard road to walk. But for those on their particularly goofy wavelength, they can be a beautiful ride.