There are far more myths in rock history than Cinderella stories, especially when you're talking about a band as legendary – and decadent – as the Who. But a rare exception took place at the Cow Palace on Nov. 20, 1973, when Who fan Scott Halpin cemented his status as one of rock's most unlikely heroes, taking the stage to fill in for drug-addled drummer Keith Moon.

This story, unsurprisingly, has taken on a number of variations throughout the years, but Halpin has set the record straight himself through various interviews.

The evening began innocently enough. The 19-year-old, then living in Monterey, Calif., met up with his friend Mike Danese and bought a pair of scalped tickets for the Who's show in San Francisco – the first stop on their Quadrophenia tour. After arriving to the venue 13 hours early, Halpin and Danese battled the swarming mobs of general admission fans for a spot near the stage as Lynyrd Skynyrd opened with their arena-sized Southern rock.

The crowd rampaged relentlessly as the Who's set began, so Halpin and Danese snuck to the side of the stage, where they watched the show. Moon, notorious for his excessive lifestyle and wild stage antics, suddenly collapsed towards the end of the band's high-octane set, during "Won't Get Fooled Again." After being revived, he was brought back to the drums, where Moon continued to play. But he didn't even make it through the next song, "Magic Bus."

After Moon passed out for a second time, Pete Townshend asked if there were any drummers in the audience. Danese pulled Halpin over to a security guard, pleading that Halpin was a proficient drummer and Who fan, and could easily finish out the band's set.

"The security guard was probably thinking he's a complete nut," Halpin told the Hoosier Times in 2006. "But all of a sudden, [promoter] Bill Graham pops up, and he sees it as a security thing. He's sort of nose-to-nose with Mike, and Mike says, 'He can do this. He's a drummer. He knows the material.' And Bill Graham looks at me and says, 'Can you do it?' And I said, 'Yeah.'"

Thrust onstage, Scott Halpin settled into the drum chair with a shot of brandy, then guitarist Pete Townshend guided the 19-year-old with cues. Halpin claimed, over the years, that he couldn't remember exactly what tracks he played on.

In fact, they raced through a loose-but-spirited take on the Howlin' Wolf jam "Smokestack Lightning," segued into Willie Dixon's "Spoonful" and then continued through a sloppy version of "Naked Eye," as Halpin fumbled through the track's dynamic shifts.

After taking a bow with the rest of the band, Halpin was led backstage, where he was thanked and given a Who tour jacket – which was later stolen. Halpin claims that a whiskey-slugging Roger Daltrey promised to send him a check for $1,000, though the money (unsurprisingly) never showed up.

Reflecting back on that fateful night, Halpin told the Hoosier Times: "To be honest, it all gets kind of foggy because it all happened so fast. I didn't have time to take it all in. All I was thinking about was not screwing up."

Scott Halpin passed away at age 54 on Feb. 9, 2008, but his brief moment in the spotlight lives on as one of rock's most remarkable fairy-tale stories.