Famed internet cat Lil Bub, whose birth defects made her one of the world's most famous and beloved online felines, died suddenly on Sunday, the furball's "dude" said.

She was 8.

"It's me, Mike — BUB's dude," owner Mike Bridavsky tweeted on Monday. "BUB has departed, she's on her way home."

It's me, Mike - BUB's dude. BUB has departed, she's on her way home. - https://t.co/8pGC6fVy4a pic.twitter.com/trkosFT2uR — Lil BUB (@IAMLILBUB) December 2, 2019

Bridavsky called his cat "the purest, kindest and most magical living force on our planet."

"BUB was cheerful and full of love laying in our bed with us Saturday night, but unexpectedly passed away peacefully in her sleep," Bridavsky said in a prepared statement.

"I have always been fully transparent about BUB's health, and it was no secret that she was battling a persistent and aggressive bone infection. Even knowing this, we weren't expecting her to pass so soon or so abruptly without warning. 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."

The polydactyl cat was born with feline dwarfism and other genetic mutations that kept her kitten-sized for her entire life, with huge eyes and a protruding tongue.

Robert De Niro pets Lil Bub, held by Mike Bridavsky, at the Tribeca Film Festival in New York in 2013. Rob Kim / Getty Images file

She was an internet sensation who frequently traveled, bringing joy to her legion of fans. She had nearly 828,000 followers on Twitter.

Bridavsky said his cat helped raise awareness and funds for special needs animals.

"But most importantly, BUB has made a huge difference in the world of animal welfare, and in the lives of millions of people worldwide," Bridavsky said.

"She has literally saved thousands of lives (both pets and humans), she started the first national fund for special needs pets, she was the subject of groundbreaking genetic and biological research, she's helped raise over $700,000 for animals in need, and has spread a message of determination, positivity, and perseverance to people all over the world."

We are very sad to hear about the loss of Lil Bub, who was well-known for her adorable and unique look.

Along with being a sweet kitty, Bub was an advocate for special needs pets and raised over $700,000 for animals in need.

She will be missed by many. ❤️https://t.co/HpXbY3DTZY — Texas A&M Vet Med (@tamuvetmed) December 2, 2019

Condolences from throughout the human and feline worlds purred in shortly after Bridavsky's sad announcement.

"We are very sad to hear about the loss of Lil Bub, who was well-known for her adorable and unique look," according to a statement from the Texas A&M College of Veterinary Medicine & Biomedical Sciences.

"Along with being a sweet kitty, Bub was an advocate for special needs pets and raised over $700,000 for animals in need. She will be missed by many."

rest in peace to sweet sweet lil' bub. she came to visit us at @Marvel HQ in November of 2012 and it was one of the most silly and fun things I've orchestrated at the office. her human was wonderful and clearly LOVED @IAMLILBUB so much. pic.twitter.com/dwIbBS4u97 — Ryan Penagos (@AgentM) December 2, 2019

Lil Bub was the subject of both a special and documentary on Animal Planet.

The cable channel tweeted on Monday afternoon: "Thank you for bringing us so much joy! You sweet, adorable, goofy creature. RIP, @IAMLILBUB. We'll miss you!"

This generation's other famed internet feline, Grumpy Cat — who real name Tardar Sauce — also passed away earlier this year.