London, UK - Fans of The 1975 were given a rather surreal surprise at their London concert with an unexpected appearance by none other than Taylor Swift.

If you were ever on Tumblr in 2014, this might be the best moment of your entire life.

The 33-year-old singer paid a surprise visit to the band's At Their Very Best tour stop at the O2 on Thursday.

Swift performed her hit song Anti-Hero off her latest album Midnights, live for the very first time.

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The audience went absolutely nuts for the performance, with many fans singing back the lyrics from the Bleachers remix that replaces "Tale as old as time" with "Taylor, you'll be fine."

Swift also covered The 1975's The City during her performance.

The 1975's ever-chaotic frontman Matty Healy promised the audience he wouldn't be up to his usual bizarre antics of kissing fans and eating raw meat in honor of the evening's special guest.

"I'm not kissing anyone in front of Taylor Swift. Have some respect. In front of the queen? It's not happening," Healy told the crowd.

The 1975 fans took to social media to share videos of their live reactions to the appearance.

"Sorry to revert to being 15 years old but TAYLOR SWIFT JUST CAME OUT AT THE 1975," a fan tweeted.

One TikTok captured the screaming and crying that naturally occurs in the presence of Queen Tay, with several fans dropping to the ground in shock.

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The surprise guest stint led many fans down memory lane, reminiscing about the infamous shirt-gate when Swift was photographed wearing a The 1975 t-shirt, to which Healy responded by donning a shirt with her 1989 album cover at a later show.

The Lavender Haze singer has continued to stay connected to the band, with her frequent collaborator Jack Antonoff producing both Midnights and The 1975's latest album, Being Funny in a Foreign Language.

Healy recently revealed that he actually worked with Swift on Midnights but their collab didn't make the final cut.

Long live the 2014 Tumblr era!