Blink-182 / Jason Merrit / Wireimage.com

"Hello!" yelled Mark Hoppus from a stage at Los Angeles' Paramount Pictures lot Thursday night. "We are Blink-182 and this is our first show together after four years of hating each other's guts!" (See a photo gallery of the show here.)

It was a moment to remember: At February's Grammy Awards, the platinum-selling pop-punk band said they would reunite -- and here they were at a corporate launch party for T-Mobile's new Sidekick LX, playing a note-perfect three-song set, as Nicky Hilton and The Hills' Heidi Montag and Spencer Pratt looked on lovingly from the wings.

The trio jumped right into Take Off Your Pants And Jacket's "Rock Show." The performance ignited a frenzy. Blink fans rushed the stage. A mosh pit formed. A fight broke out. Beer was spilled, and at one point so was a little blood.

If there was aggression on the floor, though, onstage it was all about burying the hatchet: The guys, as frontman Hoppus said, have settled their differences -- a process which began after drummer Travis Barker's near-death experience in a plane crash last year.

After a strong version of "The Feeling," the real rapprochement came on Dude Ranch's "Dammit." "I've been here for too long to face this on my own," Hoppus sang on Blink's final song of the night. "Well, I guess this is growing up."

Earlier in the evening, Weezer set the tone with their song "Beverly Hills." In a word, it was weird. There was Rivers Cuomo, rock's reclusive super-geek, singing a song about failing to fit into L.A.'s high society, while a crowd of its most televised members, including Hilton, Kim Kardashian, and assorted Hills regulars bobbed their heads and sang along.

Looking cool in thrift-store shades, Cuomo seemed to relish the irony, though, eschewing his usual guitar duties to play lead singer, while drummer Pat Wilson picked up the axe and Devo/Gn'R/NIN sticksman Josh Freese filled his duties. The band then ripped through the rest of their hits-heavy set, which included spot-on renditions of "Buddy Holly," "Pork and Beans," and a surprisingly faithful cover of MGMT's "Kids."

But even Weezer couldn't steal the spotlight from Blink-182. This was their moment and the fans agreed: 17-year-old Blink devotee Rosa Mercuriadis offered her own unique benediction after the show, when she stood solemnly, holding a drumstick that Barker had hurled into the crowd. Her once-pristine white pantyhose were covered in muck -- she had dived into the moshpit and wrestled on the floor to grab the keepsake, and she was all smiles.

Hoppus, writing on his blog later, was in similar spirits: "To be honest, it was one of the best nights of my life. Thanks to Travis and Tom. You are my brothers, and it feels amazing to share the stage with you once again."