LI fans go wild for Justin Bieber at MSG

Purple shirt on? Check. Baseball cap set crookedly atop head? Check. Ticket in hand? Check.

By now, Jamie LaSorsa, 13, of Huntington, is a pro at Justin Bieber worship, wearing the pop star's favorite color and sporting his signature baseball hat style. Tuesday night's concert at Madison Square Garden was LaSorsa's seventh quest - some quite successful - to get close to the 16-year-old singing sensation.

She's gone to "Good Morning America's" studios in Manhattan at 2 a.m. to catch a glimpse of Bieber. She was at Roosevelt Field mall last year for the now-infamous Bieber Fever fan melee and cried when the event was canceled due to the chaos. She has a picture of herself with Bieber on her Facebook page, taken when she bumped into him on a street in Manhattan before he was so lava-hot.

But Tuesday night, LaSorsa got more than she'd expected. For one, the audience was asked to stand and make the sign of a heart with their hands to be filmed for use in Bieber's documentary film about his rise to fame, set to be released Valentine's Day 2011. For another, after Bieber emerged onstage amid pyrotechnics, green lasers and white smoke, he was soon joined by the first of the evening's promised surprises: Boyz II Men. In yet another surprise, Usher joined Bieber onstage to perform "Somebody to Love." And then teen queen Miley Cyrus came out for a duet on "Overboard."

LaSorsa and BFF Meaghan McArthur, also 13 and from Huntington, came armed with cameras to Manhattan with Meaghan's mom Nancy as chaperone to hear their crush sing. They armed themselves with cameras and cell phones to post a social networking play-by-play for their less fortunate friends.

Some concertgoers were too young to even spell Bieber's name, such as Kailee Schneider, 5, of Commack. She wore a Bieber T-shirt and declared, "I like him because his hair is pretty."

Others were old enough that they were embarrassed to admit their devotion, such as Ashlee Burke and Adrianna Catalanotto, both 14 and sophomores at Northport High School. "A lot of our friends make fun of us for liking him," Catalanotto said. "They say he hasn't hit puberty."

SEE PHOTOSJustin Bieber through the years

Nancy Howser of Baldwin took daughter Gracie, 9, because she remembers the import of her own first concert, the Rolling Stones in 1973: "I just remember the whole thrill of getting a coveted ticket."