Springsteen, Lady Gaga Rock Epic Journey Duet at Rainforest Benefit - Sting and Elton John's annual fundraiser brings Madonna covers, nearly nude dancers and glittery '80s hits to Carnegie Hall...

Last night at Carnegie Hall, it was hard to imagine anything could top Sting covering the Fine Young Cannibals, Elton John leading eight dancers in minuscule bathing suits through an uproarious "Like a Virgin" and surprise guest Bruce Springsteen rocking an impassioned, nearly 10-minute Bryan Adams cover. That was until Lady Gaga emerged and Bruce began playing the opening notes of "Don't Stop Believing." The next five minutes were like a psychotic fever dream. If the sight of Bruce Springsteen and Lady Gaga embracing each other as they traded lines on a Journey song wasn't enough, Elton's nearly nude dancer squad returned as Sting, Debbie Harry, Shirley Bassey and John joined in. Springsteen said he'd never heard of the song until rehearsals, but blasted out the track's famous guitar solo before briefly joining the dance line, giving Lady Gaga a giant hug and walking offstage looking as stunned as the audience at what had just transpired.

A finale this mind-bloggling is only possible at Sting and Elton John's annual Rainforest benefit in New York. Since 1989, the two musicians have been raising money for the cause by putting on the most bizarre show imaginable. Most year's concerts begin with a rotating cast of artists singing duets on their hits, followed by a second act in which every song shares a theme. If you couldn't guess, this year's organizing principle was the 1980s. Band leader Nile Rodgers kicked off that part of the evening with his classic disco hit "Le Freak." The song is from 1978, but nobody -- especially the upper-crust crowd dancing in the aisles -- seemed to care about the slight transgression. Elton John briefly deviated from the theme to sing the Lovin' Spoonful's "Summer in the City" as a tribute to John Sebastian, who was sitting in with the band on guitar. Debbie Harry, looking ravishing in a red dress, got the 1980s dance party started for real with the Blondie hit "Call Me."

"This is one of those moments where 10 years from now you'll be saying, 'Remember when Elton did that?' " John announced before launching into a spirited cover of Madonna's "Material Girl" featuring some nice dance moves by the Rocket Man. The dance troupe arrived for an absolutely bonkers "Like a Virgin" as Sting stood on the side of the stage cracking up. "As they say in show business," Sting said, " 'Follow that!' " He came pretty close by busting out the Fine Young Cannibals' 1989 hit "She Drives Me Crazy" with incredible commitment and gusto.

The only person capable of boosting the energy in the room suddenly took the stage next. "This show needs a cardiac event," Sting said as Bruce began singing "Dancing in the Dark" from offstage. "I'm the hired gun for the evening," Springsteen announced. "Sting told me we're doing a show of '80s nostalgia. I said, 'That's easy! We're both '80s nostalgia!' "

Then it got even weirder. "This is a favorite single of mine from the 1980s," Springsteen said as he grabbed a new guitar. "I always knew there was a soul sing hidden inside of it." It took about 30 seconds before it became clear he was playing "Cuts Like a Knife" by Bryan Adams. Halfway through a very long version he stopped the song, fell down to his knees James Brown-style, and told an incredibly lengthy story about an old girlfriend who supposedly left him for a slightly more famous singer. It was hard to tell who was enjoying the bizarre performance more: the crowd, Springsteen, or Elton and Sting as they stood on the side of the stage in slack-jawed disbelief.

The evening began with Sting performing "An Englishman in New York" followed by Elton, the house band and a huge orchestra playing "Philadelphia Freedom." Elton then introduced the most anticipated performer of the evening: Lady Gaga. "This girl is everything," he said. "She can sing. She can play. She's the real deal." Looking quite dressed down and demure (at least by her standards) in a bell-shaped white dress, Gaga settled in at the piano and led the band in a note-perfect cover of "Stand By Me." "I wrote this next song for my dad," she told the crowd before launching into "Speechless." "He's here tonight." Midway through the track, Elton John strolled back onstage and sat down at sat down at another piano. "It's my other daddy!" Gaga squealed as the two reprised their Grammy performance, splicing in parts of John's "Your Song."

Sting and Mary J. Blige - who got shockingly little stage time - revived their 2003 duet "Whenever I Say Your Name" shortly before Sting's wife Trudie Styler gave a speech about the vital work of the Rainforest Foundation. After a film clip of Sting and Trudie's trip to the Amazon, Shirley Bassey belted out "Diamonds Are Forever" and "Goldfinger." The two James Bond themes have absolutely nothing to do with the rainforest, but they were fun and helped earn a ton of money for the cause, which was ultimately the real point of all the mind-blowing musical magic. "No one wants their money back! But I'm not surprised, it was one of the best shows I'd ever been in, or seen, it was incredible," Sting told Rolling Stone after the concert. "Bruce brought the house down because I told him he had to bring the house down. Gaga was incredible. I mean, forget it, it was just a brilliant show."

© Rolling Stone by Andy Greene (Additional reporting by Jennifer Vineyard)

Full setlist:

Sting - Englishman In New York
Elton John - Philadelphia Freedom
Sting/Lady Gaga - Stand By Me
Elton/Lady Gaga - Speechless/Your Song
Sting/Mary J Blige - Whenever I Say Your Name
Debbie Harry - Tide Is High
Elton John - I Guess That's Why They Call It The Blues
Chris Noth - Intro Trudie
Trudie Speech
Dame Shirley Bassey - Goldfinger
Dame Shirley Bassey - Diamonds Are Forever
Dame Shirley Bassey/Elton/Sting - Hey Big Spender
Nile And Chic (Principals) - Le Freak
Sting/Elton - Summer In The City
Debbie Harry - Call Me
Elton John - Material Girl/Like A Virgin
Sting - She Drives Me Crazy
Bruce Springsteen - Dancing In The Dark
Bruce Springsteen - Cuts Like A Knife
Bruce Springsteen And All/ Finale - Don't Stop Believing