Sabrina Carpenter joins Taylor Swift onstage in New Orleans on her one night off

Taylor Swift's Saturday night show in New Orleans came with surprises. In an orange dress, the singer told the crowd she changed the rules of her surprise set. She was going to sing a song not in her discography, but in her friend Sabrina Carpenter's music catalog.

"I think tonight I'm going to do something completely different, which is that I'm going to sing a song that's not mine, but it's somebody that I really love," the singer said to the 65,000 people in attendance before strumming "Espresso" by Carpenter. She finished after a couple of lines and paused.

"So you really love that song as much as I do?" Swift asked, smiling. "I know I'm just going on a tangent because I love my friend and I'm just so proud of Sabrina and the year she's had."

The Eras Tour crowd erupted in the Caesars Superdome as Swift grabbed her phone from a stage hand and put Carpenter on speaker.

"I'm really somewhere really loud, I'm in New Orleans on the Eras Tour," Swift said into the phone. "I just wanted to call and tell you that I sang a little bit of 'Espresso' and they said every word so loud. And I just wanted to say we all love you so much. What are you doing? Why aren't you here with us?"

Over the phone, Carpenter said, "I'm somewhere where everyone is screaming so loud."

"I'm somewhere where people are screaming so loud," Swift answered. "Can you come down to the stadium real quick? Ball park how long would that take you?"

"It would probably take me five seconds," Carpenter responded. The crowd cheered and then held their breath until Carpenter appeared on the platform in the diamond part of the stage. She strutted down the catwalk in her white dress.

Swift strummed an acoustic version of "Espresso" and sang harmony with Carpenter.

"Holy (expletive) New Orleans!" Carpenter said after the first chorus.

"Can I do it?" Swift asked in reference to the first line of the second verse, "I'm working late, cause I'm a singer.” She then dove into part of her song "Is It Over Now?" from "1989 (Taylor's Version)" and then "Please, Please, Please" from Carpenter's new album.

"She had literally one day off," Swift said at the end of the triple mashup, "She is on tour. This is crazy she came to perform for us. Will you please give it up for Sabrina Carpenter?"

Carpenter walked down the catwalk and disappeared into the stage.

Swift moved to the piano to perform a mashup of "Hits Different" from "Midnights" and "Welcome to New York" from "1989 (Taylor's Version)."

The singer-songwriter has one more performance in New Orleans. The tour will wrap on Dec. 8 in Vancouver, Canada.

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This article originally appeared on Nashville Tennessean: Sabrina Carpenter joins Taylor Swift in New Orleans on night off