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Carey, who gave birth to fraternal twins via C-section in April, performed for a few hundred fans Thursday night at New York's Gotham Hall.
Of her return she said: "I didn't realize this was a big deal."
The Grammy winner sang a number of her hits during the short performance, from 'Hero' to 'We Belong Together' to the Jackson 5 cover 'I'll Be There.'
The concert was one of four shows Thursday dubbed "Plot Your Escape: Four Concerts. Countless Celebrities. 1 Epic Night," by Caesars Entertainment. Diddy was Carey's opening act in New York, while Lil Wayne and Cee Lo performed in Los Angeles, Maroon 5 and Sara Bareilles in Chicago, and Mary J. Blige and Gavin DeGraw in New Orleans. The concerts were part of Caesars Entertainment's rewards program.
The shows happened simultaneously and were streamed online.
"We can't do anything without it being documented," Carey told the audience. "Doesn't it freak you out at all?"
Carey said if her son Moroccan was onstage, he would probably beat-box, and that her daughter Monroe would be a diva.
The multiplatinum performer thanked her fans for being there and joked: "Catch me at my real show next time."
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