Christina Aguilera dresses as Cher as stars celebrate on Halloween Eve

is still a day away, but the stars were already .

Christina Aguilera took the opportunity to pay tribute to her Burlesque costar by transforming into the diva circa the early 1990s.

The 42-year-old pop star was joined in celebrating Halloween a day early by Justin and , who looked adorable in costumes referencing the Flintstones children Bamm-Bamm and Pebbles.

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