The Web is littered with frolicking kittens, but there's only one Grumpy Cat. This photo was posted to Reddit in late 2012, but Grumpy Cat became an internet sensation in 2013, sparking a meme with captions like "I had fun once … it was awful." The mixed-breed puss, whose real name is Tardar Sauce (sic), even has her own book, branded coffee drinks, and a movie deal. (GrumpyCats.com)