The debut of The Pop-Con - the musical festival aimed at teens and tweens - turned Nassau Coliseum into Short-Attention-Span Paradise Saturday.

There was karaoke in one corner, Radio Disney-sponsored line dancing to "Party in the U.S.A." in the aisles. With two stages on the Nassau Coliseum floor, the music was nonstop for nearly seven hours. At any given moment, there were hordes of the mostly female crowd running and screaming. Oh, the screaming!

Of course, in the more than seven hours of sensory overload, nothing generated quite as much electricity as 15-year-old Canadian sensation Justin Bieber.

Bieber is on a roll at the moment, with his prime placement at the start of the new "We Are the World" and his first Top 5 single "Baby" on the charts.

His clean-cut appeal was easy to understand as he delivered his sweetened-pop version of Michael Jackson-y soul on "Bigger" and "One Less Lonely Girl," even taking on "Wanna Be Startin' Somethin'."

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He caused some swooning on "One Time." He drummed a bit. He even showed off his sense of humor. "It's good to see you guys - not in a mall," Bieber said, referring to the near-riot at Roosevelt Field mall that canceled his appearance there last year. "Just kidding."

Disney star Selena Gomez handled herself well in her 45-minute set, especially when she focused on her dancier side. Her new single "Naturally," along with the new-wavey "I Don't Miss You At All."

Long Island's Push Play ended the first phase of their career with a bang, playing the Nassau Coliseum main stage before going on hiatus as singer CJ Baran goes solo.

Of the early acts, the rockers fared far better than the popsters. Nat and Alex Wolff of the Naked Brothers Band impressively owned the stage, as they rocked through a full set of originals.

The Wonder Girls were a little disappointing, opting to show a video of their single "Nobody" to pad out their set. On a day of so many live-action stimuli, TV was just not going to cut it.