A flash mob of more than 25 dancers grooving to Fat Boy Slim's "Weapon of Choice" delighted passersby at Philadelphia's Rittenhouse Square. Witnesses said the stunt started with just two dancers and a boom box Saturday and soon expanded to more than 25 dancers moving in sync to the song before the flash mob -- a group of people organized via social media to perform a specific task at an arranged place and time -- dispersed amidst applause from the crowd, the Philadelphia Daily News reported Tuesday. "I got goose bumps," said Tracey Neill, 50, a recent transplant to the area from Idaho. "I'm sure they have these in Idaho, but I don't know where." The event brought positive publicity for flash mobs after four Philadelphia flash mobs last year resulted in violence and vandalism. Jane Irwin, one of the organizers of Saturday's flash mob, which they dubbed "Love Storm" said she and her friends decided to plan the event after watching videos of similar occurrences on YouTube.