(Yahoo! Maximum Performance) - Backstage gossip that Bill Clinton would join the Rolling Stones onstage Thursday at Rock in Rio's offshoot festival in Portugal turned out to be untrue. But the former U.S. president — sans his saxophone, but with a fleet of black-suited security guards in tow — enjoyed the big show with 80,000 or so other fans in Lisbon's majestically christened "City of Rock," as the iconic band jammed with another American icon: Bruce Springsteen.

Reprising his "Tumbling Dice" duet from the Stones' 50th anniversary celebration in Newark back in December 2012, Springsteen — who, like Clinton, was an invited VIP guest of the Stones — enthusiastically roared through his vocal parts, beaming. And as he wrapped his brawny arms around the whippet-thin Mick Jagger in a song-concluding bear hug, the Lisbon crowd went expectedly wild.

The Boss wasn't the only repeat Stones collaborator to join Jagger and company during their two-hour midnight set. Austin guitar god Gary Clark Jr., who'd also guested during the band's above-mentioned 2012 anniversary show — and fantastically opened for the Stones this Thursday on Rock in Rio's World Stage — lent his fiery blues licks to a more-than-respectable rendition of the Some Girls classic "Respectable." And the legendary Mick Taylor, who was the Stones' guitarist from 1969 to '74 (the fruitful period between Brian Jones and Ronnie Wood), and has been a regular on the group's tour during the past year, showed up for his usual epic, 10-minute-plus, three-pronged "Midnight Rambler" jam session alongside Wood and Keith Richards. Taylor returned to the stage for the show's quite satisfying, fireworks-augmented finale of "Satisfaction," shortly after 2 a.m.

Speaking of Richards, he got his usual mid-show mini-set (introducing himself by wryly quipping, "It's nice to be here. It's nice to be anywhere!"), although the songs he sang weren't his usual picks: Instead of his setlist staples "Happy" and "Before They Make Me Run," he treated the Lisbon crowd to the Let It Bleed cut "You Got the Silver" and, more surprisingly, the forgotten Steel Wheels gem "Can't Be Seen."

Rock in Rio Lisbon was only the Stones' second gig since the tragic death of Jagger's longtime girlfriend, fashion designer L'Wren Scott, which understandably derailed the band's tour two months ago. While Jagger made no mention of Scott, several of the classics he performed Thursday took on sad, poignant new meaning — particularly "Wild Horses," "Miss You," and "You Can't Always Get What You Want," the latter featuring lovely accompaniment by a local Portuguese choir.

But for the most part, the mood was revelatory and celebratory at Rock in Rio Lisbon, which marked a rare festival appearance for the Rolling Stones. As a giant video screen behind the band showed vintage footage of ecstatic Stones concert crowds from the '60s, '70s, and '80s, it was impossible not to notice how similarly Lisbon's circa-2014 audience was behaving, right down to the hippie-dippie dance moves. The aforementioned Bill Clinton, while remaining seated, definitely seemed to be enjoying the spectacle, judging from his grin as he observed from his own roped-off VIP area.

Thursday at Rock in Rio Lisbon was expected to be the busiest day of the festival due to the Stones' hyped headlining appearance, but Friday with Linkin Park and Queens of the Stone Age; Saturday with Arcade Fire, Lorde, and Ed Sheeran; and Sunday with Justin Timberlake and Jessie J are also sure to be big draws. No word yet on whether Clinton will jam during any of those sets, but if not, there's always next year — when Rock in Rio launches its first Stateside version of the festival over two massive Las Vegas weekends in May 2015.

The Rolling Stones' entire Rock in Rio Lisbon setlist was:
Jumpin’ Jack Flash 
It's Only Rock 'n' Roll (But I Like It) 
Live With Me 
Tumbling Dice (with Bruce Springsteen)
Wild Horses
Doom and Gloom 
Respectable (with Gary Clark Jr.)
Out of Control 
Honky Tonk Women 
You Got the Silver
Can’t Be Seen 
Midnight Rambler (with Mick Taylor)
Miss You 
Gimme Shelter 
Start Me Up 
Sympathy for the Devil
Brown Sugar
You Can’t Always Get What You Want
(I Can’t Get No) Satisfaction