Grumpy cat was one of the earliest internet sensation cats who rose to fame because of her unique grimace which gave her a "grumpy" appearance. Her real name, Tardar Sauce was therefore supplanted by her nickname, Grumpy Cat and propelled her to the very top of internet memedom.
Though born healthy, she would quickly develop dwarfism which affected the development of her face. Most notably her jaw which had an under bite. Her dwarfism also made her significantly smaller than her normal sized parents and siblings.
Sadly, she passed away in May 2019 to the dismay and sadness of the internet cat community.