Mystery solved: Who is that lady in blue who sang with JLo and Pitbull?

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Some fans thought they were seeing double as JLo and Pitbull took the stage to perform the official World Cup song, "We Are One." Standing next to Pitbull was another beautiful blond with looks to rival JLo's. Before they finished the song, fans were already flocking to Twitter.

Well, consider the mystery solved: The performer is Brazilian pop star Claudia Leitte.

She is the first Brazilian singer to perform an official World Cup song, and has been tweeting all about the experience. She has more than 8.1 million Twitter followers, and previously recorded a song called 'Samba' with Ricky Martin.

[Photos: More images of Claudia Leitte]

On Wednesday, in a chat orchestrated by FIFA, Leitte told fans, "It’s a very special day for me, like the day you get married, you know? That’s how it feels to me, that feeling of butterflies in your stomach."

Leitte says she has been singing since she was 3 years old, and made her professional debut at 17. She's won the Latin Grammy Best Brazilian Pop Album, Best Brazilian Sing Award and Best Band Award. Currently the lead singer for the band Babado Novo, she has also sold more than one million records as a solo performer.

"The most people I’ve sung for before was two million or so the New Year’s Eve before last, so you can imagine how it feels now that we’re talking about a billion, and a lot of people never experience something like that," she said.

[Photos: World Cup cuties - Players share tender moments with their kids]

Like JLo, Leitte is a judge on a popular TV talent show. JLo is a judge of "American Idol"; Leitte judges "The Voice" in Brazil. All of the World Cup fans professing their love via Twitter and Facebook are out of luck: Leitte is married to Marcio Quarry, who she met in high school and wed in 2006. The pair have two sons.

JLo kept fans guessing about whether she'd actually perform, but for Leitte, performing was never in question.

"With it being in Brazil, I’m the hostess, which makes it a very special occasion for me," she said, before going on to predict that Brazil will win the Cup.