GUESS/Promotional 1 / 6
GUESS/Promotional 1 / 6

A Lady Gaga look-alike caused chaos in Miami on Sunday, fooling fans, photographers and shop assistants as she toured town with a massive security detail.

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The petite blond traveled in a motorcade of four SUVs and 10 security guards when she went to a French Connection store in South Beach the day before the pop star's 25th birthday.

A source tells the New York Post, "Salespeople flocked to assist her, even helping her try on clothes for 30 minutes. She was swarmed by fans screaming, 'happy birthday!'"

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A press officer for a Guess shop in the area even released a statement about the visit, claiming that, "the crowd was getting so out of control that security needed to shut down the store so Lady Gaga could browse."

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But the visitor has since been exposed as a fake. Lady Gaga was actually celebrating her birthday a day early in Las Vegas on Sunday. Her stylist Nicola Formichetti confirmed the woman was not Gaga, writing on her Twitter.com page, "Thats (sic) not her!!"