Britney opening night homepage pic

All the Details from
Britney Spears'
Opening Night of
"Piece of Me" in Las

Courtesy Caesar's Las Vegas/Denise Truscello

Britney Spears' two year Las Vegas residency kicked off last night, and she brought out plenty of star power for her debut on the Strip!

The "Piece of Me" kicked off with plenty of fabulous costumes and celebrity friends were on hand to make sure the big night was a success. Britney pulled pal Mario Lopez on stage and whipped him during one of her songs, and other celeb pals, including Katy Perry, Adam Lambert, Holly Madison, and Miley Cyrus, showed up to support the "Work Bitch" singer.

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Also in attendance: the Spears family! Mom Lynne and sister Jamie Lynn were there, along with Jamie Lynn's new fiance Jamie King and her adorable four-year-old daughter Maddie. A source reports that the whole family took a selfie with a big Britney poster.

The show kicked off with Britney's new single "Perfume," which is more of a ballad, but quickly picked up energy as she switched to high-octane dance numbers like "Scream and Shout," "Gimme More," and even her very first hit single "(Hit Me) Baby One More Time." By the end of the show, a source reports, almost everybody in the audience was up and dancing.

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One major element of the show's look were triangles, with many set pieces arranged in a triangle shape, including one made out of red ribbon. The dance-heavy show featured plenty of exciting moves, and Britney stayed busy with eight (yes, eight!) costume changes during the show.

Although the Diamond Lounge in Vegas hosted an after-party, Brit herself didn't show - most likely, she was worn out from a full night of dancing, singing, and working the crowd and just wanted to get some rest before starting the whole routine over again!