It’s difficult to pinpoint where all of this started.

“When we were at the Palms, we had a lot of performers walk in and want to be onstage,” Frankie Moreno says over a double espresso at the Stratosphere Starbucks an hour before showtime. “It became a thing then.”

“But I remember this happening earlier,” I say, recalling nights at the Golden Nugget’s Rush Lounge, “like, when Graham Russell of Air Supply sat in …”

Moreno jumps back in. “… with the Philharmonic players,” he says, remembering the night members of the Las Vegas symphony orchestra turned up in their black stage attire and taped music charts to their backs so they could play.

“And Harry Shahoian,” I add, referring to the sometime Elvis impressionist who fronts the band Rock This Town.

The list of names builds like a pyramid scheme. “We had a night when the guys from Saturday Night Live came in, Chris Parnell and Jason Sudeikis. Parnell sang an Usher song.”

“What about Blake Shelton?” Moreno’s brother Tony says. “He did a whole set one night.”

“And Miranda Lambert. Hal Ketchum, the big country star in the ’90s,” Moreno continues, now searching his own mental contact list. “Kellie Pickler sat in with us.”

So did Joshua Bell, the violin great who took a flier from the Philharmonic after a 2008 performance and wandered into Rush Lounge when Moreno was deep into his second set. The two talked, and in a conversation that has become a family favorite, Bell asked if Moreno would want to record on his upcoming album.

“I had no idea who Joshua Bell was,” Moreno says, laughing at his own artistic naïveté. “All I knew was, he was a nice guy who had played with the Philharmonic, and he was making a CD.”

Also taking the stage at Rush Lounge that night, and for many nights at the Palms, was comic impressionist Gordie Brown. He wasn’t the only impressionist to hop onstage with Moreno, either: Greg London, whose flight of fancy through Las Vegas from 2010-’12 took him to the Riviera and LVH, joined in, too.

Sense a pattern? Maybe not. There is no pattern to Moreno’s artistic dexterity, or his willingness to envelop all variety of performers in the Las Vegas entertainment community.

“I want to be the one,” he says, “to create a scene.”

And he has with the now-recurring Stifler showcases, which have the casual air of a parlor party, the slap-dash coordination of a barn dance and the frenetic pace of a rock show at Whisky a Go Go. The event is also part of Las Vegas Weekly’s Unscripted party at the Tropicana, with the next Stifler show set for March 4 with doors at 10 p.m. and the performance at 11.

Stifler began in the wind, when Moreno invited a few entertainers to an unannounced show at the Palms to celebrate his 34th birthday in February 2012. The show overfilled the 228-seat venue, with such indelible moments as Carrot Top climbing onstage for a harmonica solo. Later, he joked that he would actually learn to play a harmonica. We were also treated to the first “impression-off,” as London and Brown toggled their best impersonations of William Shatner, Arnold Schwarzenegger and Sammy Davis Jr.

The concept of staging another all-star show boomeranged among Moreno’s family and friends, with ideas like taking over a medium-sized venue or even an outdoor space such as the top level of the Stratosphere parking garage. The Palms was eager to bring the band of merry pranksters back to the Lounge, as Moreno had set liquor-sales records at the venue during his two-month run in 2011, prior to signing with the Strat. What to call the show was up for debate, as well, with Moreno landing on the throwaway title Stifler because it was stuck in his head after he watched American Pie.

Now titled but not formally promoted, news of the next Stifler show in July 2012 spread through text, Twitter, Facebook and the odd phone call. Eventually, more than 400 people showed up, mostly performers, friends and local PR reps, along with a few people who happened to recognize an entertainer walking toward the lounge and followed out of acute curiosity. Moreno and his core band again served as hosts, and the night was a raging success—and a blatant violation of Clark County Fire Code.

And then, Stifler went dark. The show sat dormant for more than a year, as a variety of ideas floated around the Moreno camp, until last December, when Las Vegas Weekly invited Moreno to bring Stifler to Havana Beach Club at the Tropicana for the magazine’s 15th anniversary party.

The show began late with a toast by Robin Leach and a couple of long-lost originals by Moreno. John Payne of the band Asia and Raiding the Rock Vault at LVH sang Stevie Wonder’s “Superstition” backed by Moreno and his five-piece band. Violinist Bell followed with “I’ll Be Home for Christmas” (it was the holiday season, after all) and “Eleanor Rigby,” the song he recorded with Moreno on that CD years earlier. Next, Vince Neil, DJ Ashba of Guns N’ Roses and Pantera founder Vinnie Paul rumbled onstage for ZZ Top’s “Tush.”

And that was just the first 20 minutes.

Over the course of the three-hour show, a crowd of about 750 heard from some of the city’s most respected performers. Michael Grimm was called up for “Please Come Home for Christmas” and “Shaky Ground.” Smith Center Cabaret Jazz headliner Clint Holmes sang “Ain’t No Sunshine,” and former ’N Sync-er Joey Fatone pumped out “Recipe for Making Love.” Rock Vault’s Paul Shortino sang Etta James’

“At Last,” and Melody Sweets of Absinthe cut loose with “I Just Don’t Understand.” Stephanie Calvert of Starship (and now Rock Vault) did “I’m the Only One” to a chorus of cheers, and Martin Kaye of Million Dollar Quartet came up for “I Saw Her Standing There,” followed by a rendition of “Crocodile Rock” with Jersey Boys’ Graham Fenton.

The line of artists seemed endless: Jersey Boys’ Travis Cloer, Zowie Bowie’s Chris Phillips with Jeff Tortora of Blue Man Group on drums, Savannah Smith of Vegas! The Show, Aria lounge regular Patrick Sieben with Avalon Landing’s Ryan Martin on drums, and trumpet master Joey Pero. Venerable Vegas comic Geechy Guy, a regular club performer who had an impressive run on America’s Got Talent, rifled off jokes with his trademark speed, delivering punch lines with such pace that the audience could barely keep up. Even So You Think You Can Dance and Dancing With the Stars alum Lacey Schwimmer turned up for a confetti-blasted version of “Bye Bye Bye” with Fatone, the audience singing and dancing along.

At the center, always, was Moreno, the ringleader, bandleader and conductor, sitting at the piano as members of the Strip’s entertainment royalty each took a turn onstage.

How does he manage to assemble such a wide-ranging cast? “Texting,” he says. “Mass texting, and then follow-up texts.”

But rarely do you find Joshua Bell and Vinnie Paul on the same mass text. Moreno has gotten to know such performers, often at opposite sides of the entertainment spectrum, because he is trained in almost every music medium.

“It’s obvious that he is at the forefront of the top entertainers in town,” says veteran Vegas performer Clint Holmes, “and he can actually function as a performer with anybody who comes onstage. I mean, anybody. He’s not just introducing them and bringing them up. He’s included in the performance, and that makes everyone feel more inclusive, and that’s one of the keys as to why this has been so successful.”

Moreno is more measured in his self-evaluation. “I’ve played a lot of music,” he says, “and I’m willing to wrangle all these people together.”

Consequently, Moreno has become a galvanizing performer in Las Vegas, “the guy” among the current generation of Strip entertainers. But it’s not always a role he wears comfortably.

“If you consider Las Vegas a venue, a place, I don’t want to be just that,” Moreno says. “I wouldn’t want to be ‘Mr. LA,’ in the grand scope of things, because you would be just known for that.”

Already, though, he has a legacy in Vegas. “When we got here, basically, we made it our mission to be the only ones doing original music in casinos, Moreno remembers. “So, when you look at it that way … I can’t say I am responsible for more original music in casinos, but I did start swinging the machete and pissing off a lot of people so we could play original music.”

The strategy, if it can be called that, has worked, as Moreno and his brothers (Ricky, the writing catalyst and video editor, and Tony, the bassist) have crafted reams of new material just in the time Frankie has headlined at the Strat. And the show draws stars of all ilk: Earlier this month, Flavor Flav and members of Imagine Dragons were in the house (though not together, sadly).

As Paul says, “There are a lot of famous stars in this city, and the next big star is going to be Frankie Moreno.”

Moreno is not a product of Las Vegas, though. A child prodigy who played Mozart at age 5, he grew into a highly coveted songwriter in Nashville, where he learned a wide range of musical styles and how to play at least a quartet of instruments.

“In Nashville you play everything,” he says. “That’s the gist of it. It’s all music. Different cities have different scenes—Chicago has blues; Detroit has Motown. So you start to ask, ‘What is our scene?’ Let’s get a scene going [in Las Vegas] … Our music scene can be anything.”

Moreno’s years at Golden Nugget coincided with the era when his band served as the touring and studio band for Air Supply. His gigs at Rush Lounge were often promoted via text, with friends and colleagues hearing directly from Moreno or through a common friend, “Frankie’s on tonight.”

Soon, the lounge was overflowing.

“Basically I just started making friends and when they showed up, they saw I could back them up no matter what they were playing,” Moreno says. “You have to be very versatile—extremely versatile when you consider playing on a stage with Joshua Bell, then with Vinnie Paul. I mean, these guys are masters in their categories.”

Moreno stops to mull his collection of onstage collaborators.

“We have to play what they play, but it’s more than that,” he says. “When you think about it in that scope, it’s not easy. It’s really not easy calling Joshua Bell onstage, who is maybe the No. 1 living musician in the world. And the crowd is just talking and talking, and you make him do a shot, then play ‘Eleanor Rigby,’ then it’s like ‘You’re good, bro! Let’s bring up DJ Ashba and Vince Neil!’”

Holmes sees ties to Vegas entertainment history in Stifler, calling it “a new version of the Rat Pack ideal, but more modern because of Frankie.” And today, Moreno’s showcase is part of a wave of similarly styled all-star open-mic nights around the Valley. For years, Keith Thompson of Jersey Boys has presented the monthly Composers Showcase, most recently at Cabaret Jazz. Jim Caruso and Billy Stritch visit twice a year from Manhattan for their open-mic Cast Party, and Mark Shunock of Rock of Ages fronts the monthly all-star charity show Monday’s Dark at the Hard Rock Hotel. And there are plenty more, at Bootlegger Bistro, the Dispensary Lounge, Tuscany’s T-Spot and 702 Bar, where some of the top musicians from shows on and off the Strip convene for the Wednesday night Funk Jam.

What makes Stifler unique, however, is its scope, the astonishing range of national stars and Vegas stalwarts, and the span of styles stretching from country to classical.

“We’re trying to make it some epic adventure,” Moreno says, “where people walk out and say, ‘What the f*ck was that?’ How do you create that?”

He answers his own question: “By having no structure. By trying different things, and when something is not working, you move on. You just have to know a lot of groups, sub-groups, and bring those groups together.”

It helps, too, if you can really play. Because this Stifler experience is really, at its heart, a playground that just keeps growing. Even Moreno seems surprised at how these nights can turn out.

“You think there is no linear connection between all these people, but there is,” he says. “They want to showcase some amazing music and be at their finest to a bunch of people who are just great at what they do.”

And if Vinnie Paul ends the night tossing back a shot with Geechy Guy, well, then Stifler has been a success.