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Pop culture writer Harrison Brocklehurst tweeted the pictures of Welch with Swift and Charli XCX, describing them as "a love of huns apocalypse".
The comment references the popular Instagram account "love of huns", which has amassed a huge online following by embracing a very British brand of memes and nostalgia.
Waterloo Road star Welch is one of the most prominent stars of the "love of huns" page, along with the likes of Alison Hammond and Welch's Loose Women co-panellist Stacey Solomon.
One Twitter user quote-tweeted Brocklehurst's post to describe the photos as "my multiverse of madness", in reference to the onslaught of unpredictable and unlikely cameos in last year's Doctor Strange sequel.
Others noted that the Taylor Swift photo is given an extra dimension of fun by the fact that Florence and the Machine star Florence Welch also appears in the background.
"Obsessed with Florence Welch waiting politely for a pic at the Denise Welch meet and greet at the O2," one fan tweeted.
Swift made a surprise appearance on stage at the O2 Arena this week, joining Healy and the rest of The 1975 and performing her number one hit Anti-Hero, as well as a cover of The 1975 track The City.
Her appearance also made an impact elsewhere in the show, with Healy telling fans in a moment shared on TikTok that her presence meant he would rein in his controversial tradition of kissing fans at gigs.
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He said: "I'm not kissing anybody in front of Taylor Swift, have some respect. In front of the queen, it's not happening."
The 1975 released their fifth album Being Funny in a Foreign Language to critical acclaim — and the number one spot on the UK Album Chart — in 2022.
Watch: Denise Welch met her husband at Tinie Tempah's birthday party