Justin Timberlake Gangs Up With 50 Cent; Pete Wentz Crowd-Surfs; Cee-Lo And Foo Fighters Sweat It Out, In VMA Suites

... and the guest appearances are too many to count!

LAS VEGAS — "Welcome to our party, motherf---ers."

That's how Fall Out Boy's Pete Wentz kicked off his band's sweaty soiree in the Palms' Celebrity Suite, and as far as opening statements go, it probably wasn't the most eloquent ... but it was one of the most succinct.

Because that's pretty much exactly what went down up on the 26th floor, in a two-room suite that only got hotter as it got more and more packed with FOB's friends and special guests. And I mean "hotter" not in a celebrified way, but in degrees Fahrenheit, because if Fall Out Boy's party resembled anything, it was a steamy, shirt-drenching VFW Hall gig from their past (only with passed hors d'oeuvres.)

FOB kicked things off with a blaring version of the song that put them on the map, "Sugar, We're Goin Down," with Wentz and guitarist Joe Trohman spinning wildly around the postage-stamp-size stage. That was followed with a cover of Akon's "Don't Matter," and their current single, "Thnks Fr Th Mmrs," which was a thumping, sweaty ripper that ended with the band smashing its instruments and Wentz crowd-surfing.

While Wentz was being passed around the room (and just before stagehands began picking up the pieces of FOB's smashed axes), crooner (and former LV resident) Ne-Yo entered the suite and pulled himself up a seat atop the suite's bar to catch the action. Meanwhile, as Fall Out began a cover of Michael Jackson's "Beat It," Dirty, the band's omnipresent sidekick, grabbed a rather shocked-looking Brendon Urie and swung the Panic! at the Disco frontman around like a rag doll, all while members of Gym Class Heroes and Cobra Starship looked on bemusedly. (Panic later had an even more unexpected moment: They took the stage to perform, only to have their set stopped after one song by a pair of exotic dancers who were dressed as police officers, frisked the guys and whisked them offstage.

Of course, it wouldn't be a FOB party if all the band's usual associates — GCH, Cobra, Panic, Wentz's girlfriend Ashlee Simpson (who previewed her new LP the night before), the Academy Is ... frontman William Beckett, new Decaydance signees the Cab, members of the Pack, rapper Tyga, etc. — weren't in attendance. And while their collective presence wasn't much of a surprise, it was a couple of unannounced guest that really stole the show.

Like Video of the Year winner Rihanna, who positively killed a version of her song "Shut Up and Drive," with FOB as her backing band. Decked out in a black leather dress, the Bejan sensation displayed a set of pipes that rivaled Joan Jett, and backed it up with the headbanging and fist-pumping to boot. Or Lil Wayne, who joined GCH's Travis McCoy, Tyga and Urie onstage to spit fire on a remix of Fall Out Boy's "This Ain't a Scene, It's an Arms Race." (Wentz would later tell MTV News that he just freestyled the verse on the spot.) And, later in the night, Ne-Yo leapt down from his perch on the bar to sing the hook on Gym Class' "Clothes Off!"

And as if the cramped quarters and unreal collaborations weren't enough to make things even hotter, both Fall Out and Gym Class Heroes won Moonmen — for Best Group and Best New Artist, respectively — a pair of upsets that sent the room into a tizzy. The moment was a pretty good indicator of just how far Fall Out Boy have come since those VFW days: Even when they play a sweaty throwback set, it's in a suite atop a swanky Vegas casino. And they get to take home a shiny Moonman.

Down the hall, the Foo Fighters held court all evening in the Hot Pink Suite, where the air was muggy and the smell was a stomach-churning combination of cigarettes, beer and body odor. (When you try to pack 100 people into a space that could comfortably accommodate 25 tops, what do you expect?) The rockers, led by frontman Dave Grohl, kicked things off with one of their most-beloved works, "Everlong," and then launched into "Best of You."

The crowd — which included the Bravery's Sam Endicott and "L.A. Ink" tattoo diva Kat Von D — packed into the room like a can of sardines, started jumping in unison and throwing the old devil horns during "The Pretender," the first single from the band's forthcoming sixth record, Echoes, Silence, Patience & Grace.

The performance was something of a reunion for the Foos, what with ex-guitarist Pat Smear — who bolted back in 1997 — grabbing his ax to jam a few with the Fighters.

Next, Grohl summoned System of a Down mainman Serj Tankian for a cover of the Dead Kennedys' "Holiday in Cambodia." Tankian's crazed eyes raced back and forth as his soaring pipes punctuated the song's choruses.

The covers didn't end there, though: Gnarls Barkley's Cee-Lo joined the group for a rendition of Prince's "Darling Nikki," and then, after wiping the beads of sweat from his chromed dome — "It wasn't this hot in rehearsal, man ... it's a little toasty," Grohl noted — a cover of the Queens of the Stone Age's "I Wanna Make It Wit Chu." Well, maybe it would be wrong to call that last one a cover, given that QOTSA leader Josh Homme was performing along with the band.

Alas, Atlanta metal band Mastodon didn't get a chance to play Led Zeppelin's "Kashmir" with Grohl and friends, but instead were joined by Homme for one of their own tracks, "Colony of Birchmen," giving Dave a much-needed break, after loads of vigorous headbanging.

But the breather didn't last long, as the sometimes-drummer — along with Foos guitarist Chris Shiflett — re-emerged with thrash-metal legend Lemmy Kilmister for a cover of his band Motörhead's "I'll Be Your Sister." Lemmy hung around for the next song in the set, "Shake Your Blood" by Grohl side project Probot, and the entire evening was capped off with amazingly mustached Eagles of Death Metal frontman Jesse "The Devil" Hughes joining his Foo pals for a toe-tapping version of EODM's "I Want You So Hard (Boy's Bad News)."

Meanwhile, down on the Fantasy Tower's third floor, Justin Timberlake was too busy adding to his collection of Moonmen to spend much time in the Palms' Hardwood Suite, where he and VMA maestro Timbaland held it down — and were joined by some very special, and unanticipated, guests.

In the Hardwood Suite, where it was much cooler in comparison to the Foos suite, it was models, models, everywhere — it basically looked liked the world's biggest go-see. It was where all the beautiful people had congregated, in hiked-up, skin-tight mini-skirts and designer suits. But much more than that, it was the two-leveled space that played host to collaborations between JT, T.I., Petey Pablo and 50 Cent.

With scantily clad dancers clinging to stripper poles poking out of four large platforms, Timberlake first invited T.I. out and beat-boxed over the rapper's "Big Things Poppin'." He was then whisked away, leaving Pablo there to perform his track "Freak-A-Leek" solo. But the audience didn't seem to mind; for much of the evening, the suite looked more like a packed dance club than a hotel room. Timberlake then performed "Chop Me Up," after which 50 Cent showed up — Fiddy, Timbaland and Justin teamed up for "Ayo Technology," which had the fans going nuts. The audience crowded around the three, singing along to 50's new track. (Fortunately the performance didn't end abruptly, like 50's poolside pre-VMA concert.)

50 didn't need any help with "In Da Club," which he belted out from the comfort of one of the stripper platforms. 50's eyes scanned the entire crowd throughout the song, and before exiting the room, he snuck in a quick plug for Curtis, his third record, out Tuesday. And for the remainder of the night, JT was nowhere to be found — leaving reported current flame Jessica Biel all by her lonesome.

Wait — don't cash out on the VMAs just yet! From Britney's sultry comeback performance to the big winners, you saw it all — well, almost everything! Get yourself even richer with our wall-to-wall show coverage, party reports, videos and loads more at www.VMA.MTV.com. For reports, photos, video and much, much more from previous VMAs, dive into the VMA archives.