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Taking a move straight out of Britney Spears' playbook, Miley Cyrus made out with Brit's female backup dancer during the beginning of her concert.

Miley grinded with one performer before locking lips with another during Britney's first set of her “Piece of Me” show, which kicked off her residency at Las Vegas' Planet Hollywood Resort & Casino on Friday. Katy Perry, who kissed a girl and liked it earlier in her career, watched in the audience with seatmate Selena Gomez.

After smooching with the stranger, Miley later kissed a familiar face -- her latest hookup (and ex-fiance Liam Hemsworth's friend) Kellan Lutz. The 21-year-old, clad in a beige crop top that showed major under-boob, spent the wild after-party at Vegas' Beacher's Madhouse drinking, smoking and twerking on several men, including her assistant and friend Cheyne Thomas. You know, just Miley being Miley.