The rapper performed his 2002 hit during Swift's St. Louis, Missouri 1989 tour stop on Tuesday
Credit: Dilip Vishwanat/LP5/Getty

It’s getting hot on Taylor Swift‘s 1989 World Tour.

The pop star’s most recent special guest performer is a Swift tour regular (believe it or not) – Nelly!

The rapper took the stage in St. Louis, Missouri, on Tuesday night to perform his 2002 hit “Hot in Herre” – with Swift and her tour openers Haim on backup.

Swift and the sisters (who were dressed in matching white ensembles) performed the chorus complete with synchronized choreography and the track’s original voiceovers.

“Old friends,” Swift wrote on Instagram, and shared a photo of the performance. “@derrtymo has come out to surprise the crowd on my last 3 tours. I absolutely adore him.”

The 25-year-old also shared video from the epic onstage collaboration, and divulged that the cute dance routine was envisioned in a dressing room the night before.

Haim’s appearance on the star-studded 1989 stage was their last as part of pal Swift’s tour. The special moment also included a duet with Nelly and the pop star on his most recent single “The Fix.”

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The motivation behind Swift’s penchant for surprising audiences with both music and Hollywood was finally revealed earlier this week.

After a 72-year-old grandma lost her cool when Mick Jagger performed “(I Can’t Get No) Satisfaction” with Swift during her recent Nashville stop, the singer tweeted, “Why I like bringing out surprise special guests on tour,” along with a link to the video.