T he twinkly opening bars of Mariah Carey’s 1994 classic “All I Want For Christmas Is You” are as Christmassy as watching Coca Cola’s truck advert while nibbling on a mince pie. When those up-tempo bells begin to chime and Carey hits that high note, you know Santa is on his way. As, in fact, is Carey herself – she plays a festive live concert at London’s O2 this week.

Almost 25 years on, “All I Want For Christmas is You”, which Carey co-wrote with Walter Afanasieff, is regarded by many as the ultimate Christmas song, its lyrics as much a part of the season’s lexicon as “if you don’t like it, I’ve still got the receipt”. It’s so perennially popular that it even re-entered the top 40 this month.

Its message of love over materialism may be sentimental, but next to the lyrics of “Do They Know It’s Christmas?”, “Baby, It’s Cold Outside” and “Fairytale of New York”, it also stands as one of the few Christmas tunes that’s still blissfully unproblematic in 2018.

As the self-styled queen of Christmas, Carey has made the festive season a central part of her brand. Her live tour – also titled All I Want for Christmas is You – promises sequins and sexy Santa outfits galore. Over the years, she has released Christmas albums and even seasonal fragrances.

A hilarious fan-made compilation video of her saying the word “festive” in various interviews has become a classic of the viral age, spawning GIFs and memes aplenty.

Mariah Carey’s ‘All I Want For Christmas Is You’, first released in 1994

And this shareability has been a key factor in Carey’s enduring popularity, the diva reinventing her brand for the digital age. She has developed a playful public relationship with her fans and stans – the most adoring, dedicated super-fans – who she calls her “lambs”.

It was Carey’s lambs who brought the term “skinny legend” into the social media dictionary. This has no correlation to a person’s actual body shape, but represents a state of flawless confidence, simultaneously subverting and mocking the impossible expectations placed on women in the public eye.

In another meme-able moment, when asked about Jennifer Lopez in the early 2000s, Mariah simply responded: “I don’t know her”. The clip, now immortalised in GIF form, is a lesson in deeming someone’s entire existence an irrelevance.

“She’s almost as talented at throwing shade as she is at writing brilliant music,” explains 35-year-old Elliot Robinson, who has been a Mariah stan since 1993. “But then who doesn’t enjoy being a little bit shady from time to time?”

Carey’s GIF-friendly moments have helped her make the transition from the era of CDs to the online landscape – but her true fans always insist her music is their main love.

“I love that Mariah is known as a ‘skinny legend’ and she’s the shadiest diva, but the impact of her music will always be why I love her,” explains 26-year-old Jeff Ingold, who has worshipped Carey since he was 10.

“It actually really frustrates me that Mariah is sometimes more known for her persona than her music,” he adds. “When I was in my early teens, I experienced some really horrific and vicious homophobic bullying. I got through that dark period because of Mariah.”

Carey’s chart records speak for themselves. She’s twice topped the UK chart but has had 18 number one singles in the US, where “One Sweet Day” was number one for 16 weeks between 1995 and 1996, a record that hasn’t been beaten since. And her songwriting ability is her most overlooked skill: she either wrote or co-wrote 17 of those 18 US number ones.

Of course, everyone knows about her vocals. Her glass-shattering yet somehow silky smooth upper register is the stuff of legend. The sound of Ariana Grande and even Rihanna clearly reflect her vocal influence.

Mariah Carey performs at Times Square on New Year’s Eve (Taylor Hill/FilmMagic)

Carey has also proved herself a true comeback queen. Following a quiet few years, Carey returned with 2005 album The Emancipation of Mimi. Discounted by many, with the industry’s eyes drifting towards younger female artists, the album nonetheless became a global smash, selling over 10 million copies and introducing Carey to a new generation of fans.

“To see Mariah back on top after she had basically become a punchline in the music industry was unforgettable,” Ingold recalls.

2008’s E=MC2 was also commercially successful, as was Memoirs of an Imperfect Angel, notable for its lead single “Obsessed”: the Carey-penned diss track, lyrically eviscerating Eminem (“Finally found a girl that you couldn’t impress/Last man on the earth, still couldn’t get this”).

It’s not all been plain sailing, however. Her 2014 album, the ridiculously titled but criminally underrated Me. I Am Mariah... The Elusive Chanteuse, marked a commercial dip.

Carey also appeared uncomfortable throughout a stint as a judge on American Idol in 2015, later dramatically describing the job, dominated by a feud with fellow judge Nicki Minaj, as “the worst experience” of her life.

Mariah Carey gave a disastrous performance in Times Square, New Year’s Eve 2016 (Getty)

For the first time, an air of insecurity crept into her public persona. This culminated in a disastrous New Year’s Eve performance in 2016, which went viral. Carey’s set was blighted by technical difficulties, leaving her floundering. She left the stage after telling the audience: “It just don’t get any better”.

Thankfully, it did. Carey once again came back fighting, returning to the same stage the following year. Then in April this year, she opened up about her ongoing battle with bipolar disorder, a revelation that makes her achievements even more impressive.

In November, she dropped her 15th studio album, Caution, which saw a return to her unashamedly R&B roots. Carey finally seems relaxed, no longer chasing hits.

She doesn’t need to: her fans remain devoted to her, even getting her 2001 album, the soundtrack to her panned movie Glitter, to its highest sales week in 16 years following a social media hashtag campaign.

Three decades into her career, let’s enjoy Carey’s gleaming yearly lap of honour. In 2018, she is on every joke, has nothing left to prove and, for now, seems happy to be at the party. Though to her adoring fans, Mariah is far more than a novelty for Christmas – she’s for life.

Mariah Carey plays London’s 02 Arena on 11 December