Taylor Swift is continuing to impress Swifties with her surprise songs!

On Saturday, June 22, the 14-time Grammy winner stunned the audience at the second Eras Tour show in London by bringing out Paramore’s Hayley Williams to perform their Speak Now vault track “Castles Crumbling.”

In videos shared by fans inside Wembley Stadium, Swift, 34, can be seen seated at a piano with her longtime friend Williams, 35, as they perform the ballad acoustically as part of the surprise songs segment of the tour.

They have been friends since early in their careers and previously performed together in London in 2011 during the Speak Now Tour.

Before Williams graced the stage, Swift teased a special guest, keeping the fans on the edge of their seats.

“In the process of re-recording, I was really trying to reach out to artists that I’m such a fan of, or in the case of one of the albums, specifically on Speak Now, I reached out to artists who have been so influential in my music, in my writing, who I looked up to,” Swift teased.

Taylor Swift and Hayley Williams in 2010.Rick Diamond/Getty

Swift continued: “I asked an artist who I was such a huge fan of to be on one of the songs, and she said yes. London, we are so lucky because when I asked Hayley Williams to come to this show, she said yes.”

At Saturday’s show, Swift also performed The Tortured Poets Department track “thanK you aIMee” for the first time, mashing it up with “Mean” from Speak Now. During “Mean,” Swift changed the lyrics from “Someday, I’ll be livin’ in a big, ole city” to “Someday, I’ll be singing this song in Wembley.”

On June 21, Swift’s boyfriend and Chiefs tight end Travis Kelce was spotted in a VIP tent with his brother Jason and his wife Kylie Kelce. This marked the first time Jason and Kylie are seen at one of her shows. The trio returned for night two in London.

Before her shows in London, Swift played for a sold-out crowd in Cardiff, Wales, and she praised her fans for their enthusiasm on her Instagram.

“Cardiff!! My first time playing in Wales and that was truly out of control in the best way – looking out into that massive, bouncing, dancing sea of people,” the performer wrote. “I’ll never forget it. I’m absolutely living for these UK crowds.”

Meanwhile, on June 13, Swift played her 100th show in Liverpool, England, and marked the milestone by revealing when the tour would end.

In fan-captured footage of the show, Swift is seen telling the Liverpool crowd, “A lot of you are like, ‘How are you going to celebrate the 100th show?’ ”

“The celebration of the 100th show, for me, means this is the very first time I’ve acknowledged to myself and admitted that this tour is going to end in December,” she said. “That feels so far away from now, but then again, it feels like we just played our first show on this tour because you have made this so fun for us.”

She continued, “It’s taken over everything. I think I once had hobbies, but I don’t know what they were anymore because all I do when I’m not on stage is sit at home and try to think of clever acoustic song mashups.”

After her third show in London on June 23, Swift will jet off to Ireland the following weekend. On Aug. 15, she’ll return to Wembley Stadium for five more show dates.