Kate Middleton, Britney Spears and the Online Trolls Doubting Their Existence

Kate Middleton has long been a magnet for unproven rumors: She pressured an art gallery to remove a royal portrait! She split from her husband! She changed her hairstyle to distract from pregnancy rumors! She did not give birth to her daughter!

This year, speculation kicked into overdrive. Ms. Middleton — now Catherine, Princess of Wales — has lain low since Christmas. Kensington Palace said she was recovering from “a planned abdominal surgery” and unlikely to resume royal duties until after Easter. Conspiracy theorists had other, more sinister ideas. The only explanation for the future queen’s long absence, they said, was that she was missing, dying or deceased, and that someone was trying to cover it up.

“KATE MIDDLETON IS PROBABLY DEAD,” read one post on X, with the text flanked by skulls and screaming emojis.

In her invented death, the princess joins a host of other celebrities and public figures — from President Biden to Elon Musk — who scores of online detectives have declared in recent months to be clones, body doubles, A.I.-generated avatars or otherwise not the living, breathing people they are.

For many of the people pushing the falsehoods, it is harmless fun: casual gumshoeing that lasts only a few clicks, a bonanza for meme generators. Others, however, spend “countless hours” on the pursuit, following other skeptics down rabbit holes and demanding that celebrities provide proof of life.

Whatever the motivation, what lingers is an urge to question reality, misinformation experts say. Lately, despite extensive and incontrovertible evidence to the contrary, the same sense of suspicion has contaminated conversations about elections, race, health care and climate.

Much of the internet now disagrees on basic facts, a phenomenon exacerbated by intensifying political polarization, distrust of institutions such as news and academia as well as the rise of artificial intelligence and other technologies that can warp people’s perception of truth.

In such an environment, celebrity conspiracy theories became a way to take control of “a really precarious, scary and unsettling moment,” said Whitney Phillips, an assistant professor of media ethics and digital platforms at the University of Oregon.

“The darkness that is characterizing our politics is going to insert itself into even the more lighthearted articulations of speculation,” she said. “It just speaks to a sense of unease in the world.”

Pop culture history is suffused with post-mortem claims that famous dead people (like Elvis and Tupac) are still alive. Now comes the reverse.

In recent weeks, frenzied online chatter claimed that Catherine was dead or even in an induced coma — a rumor dismissed by the palace as “ludicrous.” Internet sleuths declared that photos of Catherine in cars with her mother and husband were actually another woman who lacked the princess’s facial moles.

Last week, the palace sparked more conjecture with a Mother’s Day image of the royal with her three children. Inconsistencies in the clothing and background of the portrait led to rumors that the image had been lifted from old photos in an attempt to hide her true whereabouts. By the time Catherine apologized for editing the image, the #WhereIsKateMiddleton hashtag was spreading on social media.

Another video of Catherine and her husband at a store in recent days was combed over by conspiracy theorists who said she looked too blurry, too healthy, too thin, too flat-haired, too unprotected by bodyguards to really be the princess. This week, after a video showing the Union flag at half-staff at Buckingham Palace began circulating, social media users interpreted the footage as a sign that either the princess or King Charles III, who has cancer, had died. The video turned out to be of a building in Istanbul in 2022, after Queen Elizabeth II died.

Recycled footage, easy-to-make computer-generated images, a general reluctance by most audiences to fact check easily debunked claims and even foreign disinformation efforts can help fuel doubt in celebrities’ existence or independence. There are rumors that Mr. Biden is played by several masked actors, including Jim Carrey. Mr. Musk is one of up to 30 clones, according to the rapper Kanye West (himself often said to be a clone). Last year, Russia’s president, Vladimir V. Putin, was confronted during a streamed news conference by an A.I.-generated version of himself asking about his rumored body doubles.

Peeks into celebrities’ lives were once carefully curated and rationed through a limited set of media outlets, said Moya Luckett, a media historian at New York University. Few public figures faced the kind of uproar that Paul McCartney did in 1969, when a rumor circulated that the Beatle had died years earlier and had been replaced by a doppelgänger. The supposed evidence — winking lyrics and secret messages in reversed tracks on Beatles songs — so enthralled the public that Mr. McCartney sat through multiple interviews and photo shoots to prove his presence on the mortal coil.

These days, celebrity content is widely and constantly available. Public engagement is a crucial (and often solicited) part of the publicity apparatus; privacy is not. Reality is retouched and run through filters, allowing some public figures to appear ageless while sparking unreasonable suspicions about those who don’t.

When fans believe a famous person to be in distress, cracking the case is treated as a communal bonding activity born of “a sense of entitlement under the guise of concern,” Dr. Luckett said. She calls the practice “concern trolling.”

“It’s about wanting to control how this person responds to me, wanting to be part of their narrative: I’ve already exhausted all the information that’s been out there, and now I need more,” she said, noting that a similar impulse animates the current obsession with true crime tales. “I don’t think it’s necessarily that you want to rescue or help.”

Britney Spears, fresh out of a restrictive conservatorship, shared a series of unfiltered and often eccentric posts last year that some fans read as evidence that she had been replaced by a stand-in.

So-called Britney truthers analyzed what they considered to be discrepancies in Ms. Spears’s tattoos, the gaps in her teeth and the color of her eyes. In one forum, a thread titled “She’s Been Cloned!” garnered nearly 400 comments. A popular hashtag warped one of Ms. Spears’s best-known lyrics into #itsbritneyglitch, which appeared alongside claims that a look-alike was using an A.I. filter to mimic the singer online.

Ms. Spears, who was filmed in Las Vegas this year, has repeatedly dismissed falsehoods about her demise or brushes with death. “It makes me sick to my stomach that it’s even legal for people to make up stories that I almost died,” she wrote on Instagram in February last year. A few months later, she posted (and then deleted) “I am not dead people !!!” She was quoted by People in October saying, “No more conspiracy, no more lies.”

Conspiracy theory peddlers are not necessarily believers: Some of the top voices behind voter fraud lies have admitted in court that their claims were false. Ed Katrak Spencer, a lecturer in digital cultures at Queen Mary University of London, said publicly trying to unmask a bogus celebrity could feel playful.

This month, a years-old conspiracy theory involving the singer Avril Lavigne resurfaced in a tongue-in-cheek podcast from the comedian Joanne McNally, who named her first episode “What the Hell.” The claim — that Ms. Lavigne died and was supplanted by a doppelgänger — originated from a Brazilian blog called “Avril Está Morta,” or “Avril Is Dead,” which itself noted “how susceptible the world is to believing in things, no matter how strange they seem.” In 2017, more than 700 people signed an online petition pushing Ms. Lavigne and her double to provide “proof of life.”

“Fans are themselves vocal performers; the web and especially TikTok are platforms for performance,” Dr. Spencer said. “It’s more about content creation and circulation, with all of this existing as a kind of scene. It’s about the attention economy more than anything else.”

Dr. Spencer, who worked on academic papers on rumors related to Beyoncé, said it was possible to defang celebrity conspiracy theories. In 2020, a politician in Florida accused the singer of faking her Black heritage “for exposure” and said she was actually an Italian named Ann Marie Lastrassi in league with a deep-state plot involving the Black Lives Matter movement.

Her supporters, the BeyHive, adopted “Lastrassi” as a term of endearment and incorporated it into fan-fiction and online tributes. Beyoncé herself has addressed claims that she and her husband, Jay-Z, are in a secret society, singing on “Formation” that “y’all haters corny with that Illuminati mess.”

“It all comes back to the issue of authenticity, and the crisis of confidence in people’s perception of authenticity,” Dr. Spencer said. “People are constantly questioning what they’re seeing.”