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By the look of the crowd of young girls huddled outside QVC headquarters in West Chester, Pa., at 11 p.m. on a Friday last month, it's clear there is something bigger happening at the shopping network than a sale on Joan Rivers' statement brooches. Inside, 16-year-old pop star Justin Bieber is previewing his new album, My World 2.0, for a studio audience, and a chilly rain isn't enough to deter a flock of ticketless fans desperate for a glimpse of the mop-topped teen. "I'm in love with him," explains a shivering Jackie Bugay, 15, who stands with four soaked friends, recounting how-and why-they had waited for three hours after taking two trains and a bus and walking for "like three miles" to get to QVC from their hometown 35 miles away. "He's so hot and amazing. He's not like any other singer. He has a heart," gushes her pal Madison Rivers, 12. "This is just our life," adds Gillon Lavallie, 16, who wears a Justin Bieber trucker hat and confesses, "I think about Justin all the time."

She's not alone. Though the singer and his pop-tastic songs ("Baby," "One Time") may be unfamiliar to anybody old enough to remember the early '90s, Bieber fever has become a pandemic among tweens and teens. "It's like Beatlemania," says the singer's road manager and stylist Ryan Good. "Mass hysteria. Loud screaming, crying, passing out. It's amazing." On Long Island in November, fan frenzy prevented the singer from even showing up at a promotional appearance, which police shut down; after his driver took him to an Atlanta school one day, his car was dented by girls who jumped on it trying to get closer to him. And when Bieber popped out to say hello to the diehards at QVC, the high-pitched squeals could have shattered glass.

Online-where he first attracted fans with his clips on YouTube-Bieber's an even bigger phenomenon. He has amassed 162 million views on his YouTube channel, 2.6 million fans on Facebook and 1.7 million followers and counting on Twitter; he tweets so often that when he was on vacation last December, his Twitter silence led to a rumor that he was dead. With his Biebettes organizing "buyouts" at local music stores, My World 2.0 debuted at No. 1 (making him the youngest solo male artist to top the charts since Stevie Wonder in 1963). "What I have is a once-in-a-lifetime opportunity," says Bieber, a playful kid who tinkers on a piano before kicking off his yellow sneakers and sitting for an interview in an Atlanta rehearsal studio. "And I'm having a blast."

Only four years ago Bieber was living in public housing in Stratford, Ont. (pop. 30,000), with his single mom, Pattie Mallette, 36-a former Web designer and singer in a church band who had her son when she was 19. "I worked two jobs just to make ends meet," she says. "But we had all the essentials." Bieber (who maintains a relationship with his dad, Jeremy, and two younger half siblings) began playing the drums at age 2 and eventually picked up the piano as well as the guitar, which he'd play in front of Stratford's Avon Theatre. "I wanted to go golfing with my friends and I didn't have money, so I went out [to perform]," he says. But Bieber never imagined he could become a star. "Nothing ever came out of Stratford," he says. "It's almost an impossible dream that you just don't think about." At 12, he entered a local singing competition (he placed second), and afterward Mallette posted videos from the event on YouTube for friends and family to see. Strangers from all over tuned in too, and he soon began receiving requests for other songs. "People always say, 'Did you try to get famous off YouTube?' I'm like, 'Not at all,'" says Bieber. "I was just doing it for fun."

That is until Atlanta-based music exec Scooter Braun accidentally clicked on one of the videos. "My gut was going crazy," Braun, now Bieber's manager, recalls. "So I tracked him down." Persuading Mallette to let him work with her son wasn't easy-she describes herself as "very protective"-but she relented and moved with Justin to Atlanta in 2007. "She's the best mom in the world," says a grateful Bieber, who traded his life of school and skateboarding for private tutoring and voice lessons. Before long he found himself at the center of a bidding war between Usher and Justin Timberlake, who both wanted to sign him to their labels. Says Usher, who eventually won: "There was an ultimate star quality about him. I saw that he wanted it. It was the same fire I had. He was so talented, even more than I was at [that age]."

Last May Bieber released his debut single, "One Time," and within months he was tweeting about opening for Taylor Swift, singing at the White House (he's done it twice), meeting Beyoncé at the Grammys and even getting a kiss from Rihanna. "Life is amazing!!" he wrote after the peck.

Still, he admits to celebrity growing pains. Sometimes "I wish I could go home and hang out with my friends," says Bieber, who occasionally flies best buds Chaz and Ryan to wherever he is instead. And they make sure he remembers he's still "Biebs." "I'll say, 'Can you go grab that?'" says the singer, "and they'll be like, 'No,' and hit me in the head." Mom keeps things in check too. "He can get grounded like a normal kid, get his computer taken away," says Braun. He and Mallette also make sure the teen has a day off a week-to sleep, hang out with friends-so he doesn't get burned out. When Bieber has too much free time, friends and coworkers have to be on their guard. "He likes to do pranks," says singer Sean Kingston. "My deejay was sleeping on the couch during the Super Bowl, and he put whipped cream all over his face." Usher says he's been a victim too: "Sometimes he'll call my phone and breathe in it or scream like a girl."

Could that mean an acting career may be in his future? "That'd be cool," says Bieber, who showed off his comedy skills on FunnyOrDie.com, which was turned into BieberOrDie.com on April Fool's day. Braun has been meeting with writers and producers to develop something for him. For now, there's already plenty on deck. On April 10 Bieber will be the musical guest on Saturday Night Live, he'll perform on American Idol in May, and on June 23 he kicks off a headlining tour. "I have so many things, but where'd this come from?" Bieber marvels. "Out of nowhere. Someone, like, pinch me."

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