PARIS — It all began down a narrow cobblestone road near Place de la Bastille.
An artist affixed a mosaic of a Martian from the pioneering 1978 video game Space Invaders to a wall. He used square bathroom tiles that resembled pixels.
Within the year, he had stuck 146 more to monuments, bridges and sidewalks.
He was cementing a mosaic to a church wall when the police arrested him for the first time. He was not caught when he stuck 10 up inside the Louvre.
“I was invading public space with a mosaic of a small character whose role is to invade,” said the artist, who goes by the street name Invader, during an interview in a private room of a small gallery exhibiting his work in Paris. “I had found my thing, like the great artists who found their style.”
A quarter-century later, it is hard to go more than a few blocks in much of Paris without spotting an Invader mosaic — if you look.
One peers down from a perch near the top of the Eiffel Tower. The silver eyes of another glint from the fountain in the Place du Châtelet. A red-eyed beast glowers near the Pompidou Art Gallery.
Along with Haussman apartment buildings and bridges spanning the Seine, Invader’s work has become an essential part of Paris’s aesthetic. They are an intimate part of the lives of some locals; many have formed volunteer teams to repair the damaged and replace the missing, and others plan their weekends and vacations around finding them.
His work is still technically illegal; the fear of arrest is why he first took a pseudonym. (His anonymity has since become an intrinsic part of his artistic identity, and he agreed to be interviewed only if his real name was not used.) But the Hôtel de Ville, Paris’s city hall, put the artist’s work on the cover of its poster advertising an exhibition celebrating street art. Mayor Anne Hidalgo called the artist herself to request permission.
“What will happen the next time the police stop me on the street at 4 a.m.?” said Invader, who has spent 10 nights in jail in Paris for vandalism, but never been formally charged. “Will they ask for an autograph or arrest me?”
His invasions have targeted the bottom of the Caribbean Sea and 22 miles up into the Earth’s atmosphere, using a white balloon before such a thing raised suspicion. In 2019, a copy he made of his Astro Boy mosaic, which he had put up years earlier on a bridge in Tokyo, sold for $1.12 million at an auction.
Last month, the French astronaut Thomas Pesquet sent him an email, declaring he was a fan and offering to take one of his works to the moon. “Somehow it made sense that his little aliens be up there in space, looking down at us,” Mr. Pesquet explained.
Many love the artist’s original concept that offers both nostalgia and a creepy prescience. Then there is his sheer tenacity: He has installed more than 4,000 pieces in 32 countries, including around 1,500 in Paris.
“Who embodies Paris the most? Invader,” said Nicolas Laugero Lasserre, an expert on street art and one of four curators of the city hall show.
Connoisseurs of fine art also express admiration for his work. “He’s quite sophisticated,” said Guillaume Piens, the head of the city’s spring art fair, held in the Grand Palais. “Wherever you are, when you see an Invader, you know it’s an Invader. It’s immediately recognizable.”
At a recent show, Mr. Piens positioned a stall exhibiting Invader’s work under the pillar where the artist had surreptitiously left a mosaic.
“He uses guerrilla tactics,” Mr. Piens said. “I love this. It’s part of the French psyche. We are absolutely rebellious people.”
Mystery is part of his allure, but Invader offered up a few personal details: He grew up in a suburb of Paris, a creative kid with a darkroom in the house, and graduated from the famed École des Beaux-Arts. He is “close to 50.” He is a swimmer and a vegetarian — the only cause he has mixed into his work. He sells copies of his mosaics at shows and auctions, and self-publishes books.
Over the years, his subject matter has expanded to include cultural and historical references. In Paris, some feel like an inside joke, others like a love song.
On the Rue de Louvre hangs Invader’s own Mona Lisa, next to the electric green sign of the Duluc Detective agency — a nod to when the painting was stolen in 1911. Above the exact spot where Sorbonne students led protests in 1968 looms an invader with a raised fist. From a walled-in second-floor window, an elegant Nina Simone looks down on the jazz bar where she once performed.
“I’m part of the architecture and the landscape of Paris,” said Invader, who travels by scooter around the city, admiring his own work. “And it’s something that is extraordinarily exciting for me.”
In 2014, he created an app, Flash Invaders, which allows fans to compete against one another to find his pieces, scanning them with their phones for points. There is a playful full-circle aspect to it: The computer game turned into physical art is now recaptured into the digital world. Two years before Pokémon Go was released, it set off a craze. Die-hard players organized their nights, weekends and vacations around Invader’s art. Matthieu Latrasse, a pilot currently holding the top spot of 277,000 players, asked for routes toward them.
At home, the hunt for mosaics has sent Mr. Latrasse, 43, along medieval streets and to the city’s gritty edges. “I rediscovered the city where I was born,” he said.
It was not long before die-hard flashers discovered mosaics that were damaged or missing — often from theft — and began to repair and replace them. Surprised, Invader sent instructions for what they have termed “reactivations.”
One small work near a highway has been replaced six times by a fan who loves passing it on the drive to his parents’ home.
“We are just happy and proud to contribute to his oeuvre, so they reappear,” said Olivier Moquin, a security professional who is part of a team that has reactivated up to 300 works.
Given his celebrity, Invader is now less worried about the police while working at night than he is about a random fan with an iPhone who could unmask him on social media — the ultimate invasion of private life by the digital world.
He could easily leave the streets and unveil his pieces in galleries.
But that does not interest him. “It’s like taking a drug, or like a sexual act,” he said. “When you make a beautiful piece in the city at night, and the next day you go see it, it’s extraordinary.”
Plus, he does not consider his body of work finished.
Invader agreed to a masked photo shoot before one of his pieces overlooking the Seine. In the distance loomed the turrets of the Conciergerie — a medieval royal residence turned prison.
Noticing one of his assistants cleaning the tiles, a middle-aged woman approached. Assuming they were fellow fans, she confided that she too had the app.
“Maybe one day, we will meet him,” she said. Invader, who had yet to pull on his mask, said he did not think so.
The woman nodded, and replied, “That’s what makes his charm.”
Tom Nouvian contributed research.
