Grumpy Cat, whose real name was Tardar Sauce, became an internet sensation in 2012 after a photo of her permanently grumpy expression went viral. Her unique look was caused by feline dwarfism and an underbite. The Grumpy Cat Birthday meme typically features her signature scowl paired with captions like 'I had fun once, it was awful' or 'Happy Birthday, I hate it.' It has become the ultimate way to express mock-cynicism during celebrations, solidifying Tardar Sauce's legacy as the queen of internet sarcasm and the face of anti-celebratory humor.