Calvin Klein has released its underwear campaign eight weeks into 2019, which feels inherently cruel – anyone used their NutriBullet recently? But you have to flog underwear while the sun shines, as the adage goes, and the fashion brand has roped in the dewy-skinned pop good boy Shawn Mendes to front its new campaign.

For a brand that built its image on raw sex appeal – see Kate Moss, Marky Mark, Trevante Rhodes – getting a sweet-natured cherub such as Mendes may have been a curveball, but it successfully got tongues wagging. Particularly those of other celebs.

As captured by the essential Insta-follow @commentsbycelebs, collective “thirsting”from J-Lo, Charlie Puth and Drake Bell helped make the photoshoot a talking point over the weekend. In internet parlance, “thirst” is defined as performative lustiness, and social media has become the go-to place for it. Lusting after a Calvin Klein ad – whether you’re straight, married or more of a Tommy Hilfiger guy – is fairly benign; it is supportive and affirming, not vulgar or crude. But when Instagram changed its algorithms in 2017 to rank comments from verified users higher than others, how celebrities behaved below the line suddenly became something of a spectator sport.

Instagram’s @commentsbycelebs has now gathered so much attention that it includes Gwyneth Paltrow and John Mayer among its loyal followers. Both, of course, regularly comment on their posts.

While many actors and artists still do the bare minimum on social media, the better to keep their personal lives out of the spotlight, at the other end of the scale are celebrities harnessing social media’s more meta side to get in on the joke, often at their own expense.

For a long time, social media carried a sense of obligation for celebrities: plug the tour, tease the video, tag the brand that dressed you for the red carpet. Little Mix highlighted the perils of this strategy in 2016. While plugging their new fragrance on an Instagram post, they accidentally pasted the entire email from (presumably) management, which included the opening line “How’s this copy Jade”.

Now, though, social media is where many celebrities let their hair down. It is where Chrissy Teigen can troll her husband, John Legend, by insisting he looks like the animated aardvark Arthur, and where Tom Holland can wish his Spider-Man co-star Jake Gyllenhaal a “Happy Valentine’s Day boo <3”. And when The Good Place’s Jameela Jamil criticised Cardi B for promoting detox teas – “I hope she shits herself” – Cardi responded on Instagram by pointing out that, were nature to suddenly call, she could simply go to the toilet in a nearby bush.

Celebrities getting meta shows us how crucial an online identity is even for global artists. Ariana Grande used Twitter to call out the Grammys producers who criticised her for not performing or attending. Later, she posted a photo of her on the floor of her house wearing the Zac Posen dress she had planned to wear to the ceremony. Such is the power of social media now, the fact she won a Grammy ended up being the least interesting part of her weekend.