Grumpy Cat died at home following complications from a urinary tract infection on May 14, 2019. One of the most famous cats in the world. Tardar Sauce (April 4, 2012 – May 14, 2019), commonly known as Grumpy Cat, was an American internet celebrity cat. She was known for her permanently "grumpy" facial appearance, which was caused by an underbite and feline dwarfism. RIP Grumpy.