One of the most anticipated moments from Taylor Swift’s Eras Tour concerts is the acoustic segment “Surprise Song.” It comes late in the show, between sections devoted to “The Tortured Poets Department” and “Midnights,” the final chapter.

Swift often brings special guests to help sing the surprise songs. No guests were present on Friday, October 25, the first of three nights of the Eras Tour at Caesars Superdome in New Orleans.

But on Saturday she managed a big surprise.

“I think I’m going to do something completely different tonight,” she said at the start of the acoustic section. “I’m going to sing a song that’s not mine, but it’s someone I really love. So I want to see how loud you can sing the song.”

“It’s stuck in my head. It would make me feel good to know that 65,000 other people have this song in their head the same way I do.”

With that, she began singing “Espresso” by Sabrina Carpenter, one of her previous opening acts who is now headlining the arena.

“I love my friend and I’m just so proud of Sabrina,” she said. “She was the opening act for the Eras Tour earlier this year. This year she absolutely took off. There are no tickets for her tour. Her album is constantly No. 1. I know she would really like to know.” How loud did you sing that song? Is it okay if I call her?”

She pulled out her cell phone, called Carpenter — who is currently headlining her own Short n’ Sweet Tour — and held the phone up to the microphone.

“Is there a chance you could get out and put some clothes on and just come out and sing with me?” Swift asked. “How long would it take you?”

Carpenter replied, “It would take me about five seconds.”

With that, she rose from below the stage in a short white babydoll dress as the arena erupted in screams.

With Swift playing an acoustic guitar, they joined forces for “Espresso.”

“Can I do that?” Swift asked.

“You can do it,” Carpenter replied.

“Oh my God, I’m about to do it,” Swift said, then added the infamous Carpenter line: “I work long hours because I’m a singer.”

They mixed “Espresso” with Carpenter’s “Please, Please, Please” and the deep 1989 Swift-era cut “Is It Over Now?” while fans screamed the lyrics from their seats.

After her “Espresso” mash-up, Carpenter stalked down the stage and disappeared.

Carpenter performed her own show in Tampa on Friday and is scheduled to perform at the Toyota Center in Houston on Sunday.

“She literally has a day off,” Swift said. “She’s on tour. It’s crazy that she came to perform for us,” Swift said, adding, “Saturday night has been fun so far, right?”

It was even more fun when Swift sat at the piano and mixed “Hits Different,” a bonus track from “Midnights,” with “Welcome to New York” from “1989 (Taylor’s Version).”

The rest of the show featured the same songs from “Midnights,” which usually closes the Eras tour.

Surprise songs on Friday evenings

On Friday, the first of Swift’s three sold-out nights at Caesars Superdome in New Orleans, she went to perform her debut album “Our Song,” which she paired with the acoustic guitar mash-up “Call It What You Want” from Reputation.

What followed was a piano mashup of “The Black Dog” from Tortured Poets Department and “Haunted” from 2010’s Speak Now.

This past weekend in Miami, Florence + the Machine’s Florence Welch made a surprise appearance with Swift to sing “Florida!!!” after previously appearing on the recorded version.

Nola.com reporters Chelsea Shannon and Lauren Walck contributed to this report.