Taylor Swift And Idina Menzel Sing 'Let It Go' in Costume on Halloween

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This may be the best Frozen collaboration yet!

Taylor Swift loves bringing celebrities out as special guests on her 1989 World Tour. She just can’t let it go.

The 25-year-old singer surprised fans at her final U.S. show in Tampa Bay, Florida, on Saturday, this time bringing Idina Menzel on stage to sing a rendition of "Let It Go" for her last stop on the tour.

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Even better, the two were dressed in full-on Frozen costumes -- Swift as the lovable snowman Olaf, and Menzel as ice princess Elsa, her character in the Disney film. Swift's back-up dancers were in on it, too, all dressed as reindeer. It was Halloween, after all.

The "Wildest Dreams" singer later took to Instagram to document the memorable night.

"Frozen totally happened tonight," she captioned the photo. "And 55,000 people sang 'Let it Go' so loudly, it nearly took my breath away. Good times, @idinamenzel."

WATCH: Kristen Wiig & Ellen DeGeneres Sing 'Let It Go'

Menzel followed it up with a video from their performance, showing a quick change that happened near the end of the song. The 44-year-old and Swift ripped off their costumes, revealing ensembles that were more formal.

"That was definitely an out of body experience," Menzel wrote. "Or out of Elsa's body experience!"

"After the costume change, while the crowd was singing," Swift captioned another photo of her and the Broadway star.

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The popstar also took to Twitter to thank Menzel and Alessia Cara -- her other special guest of the night -- for helping her end the tour with a bang.

"Sharing a stage with @alessiacara and @idinamenzel was the perfect way to end this amazing chapter," she tweeted. "Thanks ladies."

Swift isn't the only one who's a fan of the catchy tune. Last September, Kristen Wiig appeared as a guest on The Ellen DeGeneres Show and delivered a hilarious karaoke-esque version of the song with the talk-show host.

Watch the video below to see more.