Looking at Andrew W.K. in his sweat-stained white jumpsuit, wildly pumping his fists and flailing about the small stage of Slim's in San Francisco like some convulsively whacked-out madman, even the most accepting rock fan couldn't help but wonder: Is this guy for real?

It's a question that has sparked much debate ever since the artist formerly known as Andrew Wilkes-Krier burst onto the scene with his 2001 major-label debut, the raucous Party Hard E.P. Indeed, W.K. is a throwback to the days when hair-metal dinosaurs roamed the planet, and the Billboard charts were dominated by the likes of Motley Crue, Quiet Riot and Judas Priest.

With chest-length brown locks that fly every which way as he thrashes about, a supporting cast of muscle-bound headbangers who seem to have arrived via time warp from the late '80s, and a catalog of pop-metal anthems espousing his simple, hedonistic philosophy ("Party Hard," "Party 'Til You Puke," "It's Time to Party"), Andrew W.K.'s whole act seems rife with tongue-in-cheek irony. Like a 21st-century Spinal Tap, he and his bandmates turn the amps up to 11 and kick out feather-brained -- albeit supremely catchy -- party jams that recall the Ramones and the Misfits.

But if W.K. subtly winked at fans on his 2001 full-length debut, the frenetic I Get Wet, there wasn't a hint of that in his performance Tuesday night at Slim's, where he delivered a blistering hour-long set that threatened, on several occasions, to bring the house down -- literally.

Hurling himself about with no apparent regard for his own well-being, WK whipped his mostly adolescent audience into a frenzy, urging them to form a tight, circular mosh pit and encouraging them to join him on state for a few seconds of unadulterated mayhem.

They were only too happy to comply. As soon as W.K. took the stage, kicking off the evening with a bruising rendition of "It's Time to Party," the crowd surged to life, as impatient fans pushed and shoved their way into the widening pit, either to be sucked into it or tossed violently out. Throughout the set, rabid teens clawed their way onto the stage, taking brief timeouts from the pit before hurling themselves back into the swirling sea of humanity.

Not that the band seemed to mind. Ever the gracious hosts, they gleefully deferred to their fans, allowing them to thrash about the stage and borrow the mikes for a few seconds of karaoke-style singing. To his credit, W.K. never turned away a fan seeking a hug or a snapshot, and even managed, with an endearingly goofy grin, to perform two songs with a pile of teenage boys clinging to his back.

By the time he finished his set with a typically aggressive version of "Party Hard," during which dozens of fans rushed the stage, W.K. was ready to return the favor. Dousing himself and most of the crowd with water, he dove into the pit, riding the sea of outstretched hands until he could crowd-surf no more. After stopping to greet and embrace most of the patrons, he made his way back to the stage to bid his panting, sweating, screaming fans farewell.

Some had fainted during the show, while others had been carried off by security guards, some with nasty gashes and bruises. But on an otherwise quiet weekday night in San Francisco, Andrew W.K. made sure that everybody got a little bit wet. -- Rossiter Drake