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Christina Aguilera surprised Sabrina Carpenter and her fans at the LA stop of her "Short n' Sweet" tour.
According to Entertainment Weekly, Sabrina looked genuinely surprised when Xtina appeared on stage singing her song, "Ain't no other man."
They note that when Sabrina saw what was going on she mouthed the words, "What the f---?"
EW notes that the two sang "What a Girl Wants," which they sang together earlier this year.
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