Had Choupette deigned to attend the Met Gala, she would have joined many other immaculately groomed guests with elite pedigrees. But she might have been the only one to require a litter box.

Choupette, the Birman cat once owned by Karl Lagerfeld, led a life of decadence by the designer’s side. She flew private. She had an iPad. She took her meals from three Goyard dishes, according to Mr. Lagerfeld: “one for water, one for her little croquette and one for her pâté.”

Since Mr. Lagerfeld’s death, Choupette has remained an obsession of fans and fashion insiders, becoming something of a four-legged embodiment of the designer’s legacy. In Vogue’s recent tribute to Mr. Lagerfeld, she lolled over the arm of a windswept Naomi Campbell.

She received an invitation to the Met Gala celebrating her onetime owner, according to her agent, Lucas Bérullier. (Like anyone who’s anyone in fashion, Choupette has an entourage.) But on Monday, she officially sent her regrets.

“Many people invited me to walk the red carpet of the #METGALA2023 in tribute to Daddy, but we preferred to stay peacefully & cozy at home,” the Instagram account @choupetteofficiel said. “We pay tribute to my Daddy every day since his parting and we are very moved to see one more day dedicated to him.”

Choupette was born Aug. 15, 2011, and at first belonged to Baptiste Giabiconi, a French model and muse of Mr. Lagerfeld’s. Mr. Lagerfeld developed a deep affection for the Birman while cat-sitting over Christmas that year. “When he came back, I told him that the cat was not returning to his house, and I kept it, this kind of genius creature,” Mr. Lagerfeld told The Cut in 2018.

He doted on her unrelentingly. Choupette stayed in his suite at the Mercer and was flown to New York City and St.-Tropez, sometimes with permission to roam freely on the plane, according to “Paradise Now,” William Middleton’s biography of Mr. Lagerfeld.

“He was so extreme in every single thing he did,” Fran Lebowitz told Mr. Middleton. “So, if he’s going to have a cat, he’s going to have a cat that has a diamond necklace.”

Despite lacking the leggy physique of many cover stars, Choupette fronted international editions of Vogue alongside Linda Evangelista and Gisele Bündchen. But she did not turn up her nose at commercial work, appearing in campaigns for Opel automobiles and, naturally, Chanel.

“She is a famous beauty,” Mr. Lagerfeld told Women’s Wear Daily in 2012. Choupette is the creamy shade of one of Mr. Lagerfeld’s couture bridal looks for Chanel, with an oatmeal-colored patch of fur softly splashed across her face. Her eyes are believed to be the inspiration for a shade of blue in Mr. Lagerfeld’s Chanel collections.

In addition to the questions raised by her upper-crust lifestyle at a time when many were struggling financially, she was often the subject of gossipy headlines. “Karl Lagerfeld Would Marry His Cat Choupette if It Were Legal,” Vanity Fair declared in 2013. (Mr. Lagerfeld had recently avowed his love for Choupette in a CNN interview and lamented that marriage between humans and animals was not an option.)

After Mr. Lagerfeld died in 2019, rumors circulated that Choupette might become his heiress. Bloomberg ran a story on the French and German laws that would prevent a pet from inheriting millions. “Lagerfeld’s Cat Won’t Get Her Paws on His Fortune,” the headline concluded.

In recent years, Choupette has lived in Paris with her nanny, Françoise Caçote, a former housekeeper for Mr. Lagerfeld. She posed beside a bottle of Champagne on her 11th birthday, gazing out the window of a grounded jet.

Ashley Tschudin, who runs “Choupette’s Diary” fan pages on Instagram and Twitter, said that fans appreciated living vicariously through images of the pampered pet. Her attendance at the party of the year would be no exception.

“This cat lives a better life than most humans,” Ms. Tschudin said.