AceShowbiz - Taylor Swift has successfully granted one of fans' wildest dreams. The "All Too Well" hitmaker made a surprise appearance during HAIM's sold-out concert in London's O2 Arena.

On Thursday night, July 21, Taylor was brought out by HAIM sisters for the pop rock band's penultimate show of their tour's European leg. The superstar took the stage alongside the group in matching leather pants and a black crop top.

For the night, Taylor and HAIM delivered an edgy mash-up performance of the remix of "Gasoline", which originally appeared on the expanded edition of the sisters' June 2020 album, "Women in Music Pt. III", and Taylor's iconic solo song "Love Story". They ended their performance with an adorable group hug, as seen in a viral video of the performance shared to social media.

The updated version of "Gasoline" featured Taylor on harmonies in the chorus, plus taking the reins on the second verse. "You did me bad/ And I did it back/ You needed a**, well, what's/ Wrong with that?" she sings.

While onstage, Taylor said that their idea to collaborate during the concert was all part of a master plan to get the crowd "to sing the loudest you have sung all night." She added, "Which is a big challenge because you have been singing very loudly -- extraordinary work."

Taylor then noted that it's been a while since she has performed in concert, while also shouting out HAIM's sold-out status at the O2 Arena. "I haven't been on stage in a very long time," she told the audience. "It's nice…it's nice, it's very nice [to be back]. When I heard my girls were playing in London at the O2, I thought, 'I'm going to have to see that.' And it looks like there's about 20,000 other people who also thought that."

Before taking the stage, Taylor shared a hilarious video to her TikTok page, in which she's seen sneakily copying HAIM's onstage outfits. "Hitting copy paste on your friends' looks like," the Grammy-winning singer captioned the video, which was soundtracked by Children's Song Factory's "Copycat" song.