For the fashion commentariat, the front row used to be everything. But these days, if you have something to say, you’re better off infiltrating the runway itself.

That was the thought of Marie Benoliel, a 28-year-old professional gate-crasher who clambered onto the catwalk at the Chanel show in Paris on Monday only to find herself in a confrontation with the model Gigi Hadid. In an interview, Ms. Benoliel, who prefers to go by her stage name Marie S’Infiltre, explained her intention: to have fun.

“It goes too far to take seriously something that is not serious,” she said of the fashion world. “We’re talking about clothing. It has to be joyful, it has to be funny, it has to make people happy. And I think nowadays fashion doesn’t make people happy. It makes people ridiculous and pretentious.”

(Chanel was the second show she crashed over the course of this fashion week. Etam, a French lingerie brand, was first.)

For the stunt, Ms. Benoliel borrowed a Chanel suit that her mother had purchased in 1986 “with her first salary, because she’s a fashion addict,” she said.

Lacking an invitation, which unknown guests are typically compelled to produce at the entrance, she waited until it was as busy as possible. Three times, she was turned away. She almost gave up, but decided to try one more gatekeeper, and acted as stressed out as she possibly could. She was let in, along with a friend, Elena, who just wanted to watch the show.

“I’m really used to lying,” Ms. Benoliel said. “It’s part of my work.”

Once close to the catwalk, surrounded by fashion editors and a smattering of famous people including Cardi B, Sting and Anna Wintour, she hesitated. Then, as the end of the show appeared imminent, she thought “why not.” Ms. Benoliel walked as slowly as possible to the front, then made a dash and climbed up to the catwalk. There was a momentary disruption but she soon fell in line. Her houndstooth suit fit seamlessly enough into the show’s aesthetic that apparently even security guards had trouble identifying her as an impostor. (Tweed suits have long been a Chanel runway staple.)

Her intention was to take out a cigarette and smoke it, until Ms. Hadid stepped in and pulled her aside, leading her offstage. (A publicist and agent for Ms. Hadid did not immediately respond for comment.)

“She was rude,” the prankster said. “Then, after, there were three models that wanted to fight. I didn’t understand why she was like this, so aggressive. Of course she doesn’t know me. I can understand that she wanted to protect her friends.”

She added: “I think it’s really funny and I love Gigi and I think now we can be close friends. She thought I was a crazy girl. But she’s right. She’s right actually.”

Chanel offered a statement: “This person is a comedian known for this type of prank. She had crashed another runway recently. Her presence on the catwalk was not planned.”

Ms. Benoliel was not the first person this fashion season to use the runway as a metaphorical platform. During Milan Fashion Week, the model Ayesha Tan Jones, who identifies as nonbinary, staged a silent protest while walking for Gucci, holding their palms up with the phrase “mental health is not fashion” scrawled in marker. (The show featured several models wearing straitjackets.)

It is not easy to sneak into a fashion show, said Dan Mathews, the senior vice president of PETA.

“We’ve crashed dozens of shows, there’s a whole routine,” he said. “We decide in advance, like ‘Are we going to hit the runway after the seventh model?’ It’s very planned out.”

Mr. Mathews, who once dressed as a priest to get into a fashion show, said sneaking in usually involves planning a week in advance and compared it to “a 007 operation.”

He noted that PETA’s motivation in crashing the runway is to publicize animal rights, while runway crashers today seemed more intent on drawing attention to themselves.

Ms. Benoliel, who studied at the The Paris Institute of Political Studies and who in 2017 infiltrated a rally for the far-right leader Marine Le Pen, said she is not a moralist.

“I hate people who say ‘you’re good, you’re bad,’” she said. “I don’t care about this.”

Alissa Khan-Whelan, part of the team behind the image of the egg that in January broke the record for most liked Instagram post, said that it was effective that the Chanel infiltrator avoided stating a message outright.

“Instead of going out there with a big sign and saying, ‘This is what I think and this is what you should think,’ she’s just causing chaos and people are questioning it themselves,” said Ms. Khan-Whelan, who on Wednesday was engaged in a stunt involving an ice sculpture of the climate activist Greta Thunberg melting in London’s Trafalgar Square.

With a following of 231,000 subscribers on YouTube and 219,000 followers on Instagram, Marie S’Infiltre is moderately well-known. She gained a surge of attention after the stunt but seemed most excited about the act itself.

“I’m not going to tell you it’s something that makes me more powerful,” she said. “Chanel is of course the most prestigious brand. I wanted to get inside the show to put my little touch to say ‘yeah this is important, this is art, but we can be joyful.’”

She added, “I look like a grandma with the suit but I don’t care, it’s Chanel,” addressing her outfit. “Bye bye, Lily Rose. Bye bye, Cara Delevingne. I’m here.”

Daphné Anglès and Elizabeth Paton contributed reporting.