From PEOPLE Magazine Click to enlarge
One Direction devotion is impossible to resist-even for those who are used to being on the other side of fan adulation. "I love them! I love them!" Taylor Swift told PEOPLE after watching the guys perform at the Nickelodeon Kids' Choice Awards in March. "Me and all of my friends were so excited-we had an all-out dance party when they were up there. I just loved it!"

That kind of intense passion (usually paired with screaming, tears or even fainting) has been building for the boy band-made up of Harry Styles, Louis Tomlinson, Zayn Malik, Niall Horan and Liam Payne-ever since they were formed on the U.K.'s X Factor back in 2010. Though they didn't arrive in the U.S. until earlier this year, for many Directioners, they needed no introduction: Savvy teens discovered them online long before they became international celebrities. "We owe a lot of our success to Facebook and Twitter," Zayn said. "A lot of our fans are on there. That's how we connect with them."

As a result, when their debut album, Up All Night, was released in March, it landed at No. 1 on the Billboard 200-a history-making feat for a British group (yes, that even includes the Beatles). Just how big is the One Direction phenomenon? At the BRIT Awards (the U.K.'s version of the Grammys) in February, they edged out the seemingly unbeatable Adele to win Best British Single (for their song "What Makes You Beautiful"), a prize determined by fan votes. Their videos have been watched nearly 300 million times on the music site Vevo. Tickets to their December concert at New York City's Madison Square Garden sold out in less than 10 minutes. And when they were scheduled to perform on Saturday Night Live, hundreds of fans spent several nights sleeping on the sidewalk in an attempt to get tickets to the show. (They've also appeared on Nickelodeon's iCarly and performed for 10,000 fans at a Today show concert.) "We haven't seen this kind of boy-band mania since 2002," says Billboard editor Joe Levy. "This is state-of-the-art pop music buffed to an even higher gloss than usual."

One Direction's goal, in fact, is to set themselves apart from their boy-band predecessors. "We're trying to do our own thing," Liam said. In Zayn's words, "We're five normal lads: We're not massively ripped, we don't have amazing bodies, and we freely admit we can't dance."

Don't worry, Zayn, no one is screaming for better choreography or more muscles. But there will be plenty of screeching when the boys continue their U.S. tour in May and then return stateside in 2013. As for long-term plans, Harry doesn't want to make too many predictions. "A year ago we would never have expected any of this stuff that's happening now," he told PEOPLE. "We just want to keep working hard, making sure we keep on delivering the best we can, having fun, and we'll see what happens."