Today is the 50th anniversary of one of the wildest rock & roll shows of all time: the day Keith Moon took way too many drugs and was rushed to the hospital and a teenage fan sat in for him and jammed with The Who.

The story is not told enough, though when it is, it's often told wrong.

November 20, 1973 was not the first night of The Who's Quadrophenia Tour, it was the first night of the US leg. They had played a half dozen shows earlier across the pond, some poorly.

The first few gigs in October were hampered by technical issues because the band had decided that instead of additional musicians to play the complicated instrumentalization Pete Townshend had layered on the album, they'd play along with pre-recorded backing tracks as well as a click-track for the drums.

This did not sit well with the notoriously erratic Moon who rarely played songs the same way twice and was now stuck with a robotic metronome. The band had scheduled two days of rehearsals to familiarize themselves with the backing tracks but one of the days was cut short when singer Roger Daltrey punched Townshend so hard he thought he had killed him.

In his autobiography, Daltrey said the band was on edge in part because their new US label, MCA had booked them to film an advertisement for the album and tour and things were going at a snail's pace. Daltrey objected to the filmmakers, saying the valuable time needed to be used on the music, and Townshend, allegedly drunk according to the singer, told him to zip it and took a swing at him with his Telecaster.

When the sloppy musician delivered another blow, Daltrey ducked and countered with an uppercut. An ambulance was called and Daltrey sat in the back next to Townshend and apologized on the way to the hospital.

The MCA Records exec asked Moon if the band was always like this, the drummer said, "no. Today is one of their better days.’”

Funny, because it's true.

A few weeks later the band is about to play San Francisco's Cow Palace, the legendary venue where the Beatles kicked off their first US tour.

Lynyrd Skynyrd were the openers, supporting their debut album, (pronounced 'Lĕh-'nérd 'Skin-'nérd), which would go triple platinum thanks to "Free Bird," "Gimme Three Steps," and "Tuesday's Gone." It was their first big time tour.

While Skynyrd was playing that infectious southern rock and pleasing the crowd with the likes of "Simple Man," Moon was backstage easing his nerves with a local beauty who shared some tranquilizers with him chased it down with brandy.

How do we know this?

Because near the beginning of The Who's set, the young lady had a seizure and was taken to the hospital.

Being a freak of nature, Moon made it 15 songs before the cocktail of what some claim to be PCP or monkey tranquilizers mellowed the drummer out so much he decided to rest his eyes right there at his kit.

"We're just gonna revive our drummer by punching him in the stomach," Townshend told the crowd of about 15,000 that fall night.

"He's out cold. I think he's gone and eaten something he shouldn't have eaten. It's your foreign food," Townshend quipped. "The horrible truth is that without him, we aren't a group."

A half hour later Moon was revived thanks to was awake and alert. He hopped on his throne and began the rollicking beat to "Magic Bus," and never finished it.

“He fell backwards," the SF Chronicle reported, "and had to be dragged offstage.”

The remaining members tried to soldier on by performing the Tommy anthem "See Me, Feel Me" without drums, but Pete was right, without their drummer, they were... what? Who?

Off stage the band asked Skynyrd's drummer Artimus Pyle if he could fill in. Terrified of sitting behind the hallowed kit of Keith Moon, who had just keeled over, twice, behind that thing, Pyle passed.

So Pete did something you only see in movies - he asked the crowd if anyone can play drums. And then specified, "we need somebody good."

This was not a modern day rock show where the Foo Fighters could just call up a guy with Kiss makeup on and the dude shreds. This was real life.

Nineteen-year-old Iowan, Scot Halpin was at the show with his friend. They drove up from the sleepy beachside town of Monterey without even a ticket. They had gotten lucky with a scalper outside the Cow Palace and made their way to the front.

Scot's friend raised his hand and pointed at his buddy who spelled his name with just one "t." Legendary rock promoter Bill Graham, who was running the show had Halpin come up on stage.

On his way to the kit, he was given a shot of booze, downed it and when he sat down at the set he was shocked at how huge Moon's drums were.

“It was ridiculous," Halprin said in an interview later. "The tom-toms were as big as my bass drum.”

But unfortunately for Halprin, once he started getting into the first number, Howlin’ Wolf’s "Smokestack Lightning," he realized he had another problem: "any place you could hit there would be something there. All the cymbals overlapped."

Willie Dixon's "Spoonful" was next and then the final tune, the Who's "Naked Eye" and the long night was over.

John Entwistle and the band embraced Scot, they all took a bow to the crowd, and Pete did some Rockettes high-kicks as they all stumbled off the stage.

Moon died five years later at 32 years old. And sadly, Scot died in 2008 at 54 from a brain tumor.

On a whim, Scot's wife decided to write Townshend to tell him of the news of his passing and to her surprise, Pete wrote back with such a lovely letter that she read it at his funeral.

“Scot is often in my mind and always with the greatest gratitude and affection,” Pete wrote.

“He showed such youthful courage and humour standing in for Keith Moon that fateful day. Scot played so well too. He played drums brilliantly, smiled and went home. I measure my life by great and good people I have occasionally met. Scot is one of the great and good ones."

Several months later a blog was created as a memorial to Scot. The Who posted about it on their website in a classy way.

The blog eventually grew to become the T. Scot Halpin Archive which you can find here.

Will The Who tour soon? Perhaps, but in April, Daltry said he doubts they'd return to the States.

"I don’t know if we’ll ever come back to tour America," he told USA Today. "There is only one tour we could do, an orchestrated Quadrophenia to round out the catalog. But that’s one tall order to sing that piece of music, as I’ll be 80 next year. I never say never, but at the moment it’s very doubtful."

Keep your eye on The Who's website for updates.