"I truly believe that she willingly made the decision to leave her failing body so that our family would not have to make that difficult decision ourselves," Bridavsky added in the caption, which accompanied his first and final photos with her.
In 2011, Lil BUB was discovered as a kitten in a rural Indiana toolshed as the runt of a feral litter of cats. She was born with "a multitude of genetic anomalies," according to her website.
The feline was a "perma-kitten," meaning she retained her kitten-like features and remained "kitten sized" for her entire life. She also had an "extreme case of dwarfism," so her limbs were disproportionately small in relation to the rest of her body. Her lower jaw was much shorter than her upper jaw, and her teeth never came in, which lead to her signature hanging tongue.
She first rose to fame when Bridavsky posted about her on Tumblr, CNET reported. At the time of her death she had over 2.4 million Instagram followers. Lil BUB has been featured on various types of merchandise and stuffed toys, appeared on television many times, and even has her own book.
The famous pet and her owner also regularly used her platform to advocate for other animals. Her national fund for special needs pets, Lil Bub's Big Fund for the ASPCA, has helped raise hundreds of thousands of dollars for animals in need since 2014, according to her website. She was also "the subject of groundbreaking genetic and biological research," according to Bridavsky's post.
This year has not been a good one for internet cats. Grumpy Cat, the world-famous feline whose signature frown is used in memes everywhere, died at age 7 in May. Despite care from top professionals and loved ones, her family said she died following complications with a recent urinary tract infection.