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Koko, the world's most famous gorilla, is a cat lover. Whatever you think of her abilities to communicate via sign language, there's no doubting that she treasured her tailless kitten All Ball. Sadly, All Ball died after being hit by a car; when the news of Koko's mourning broke, as TIME noted a few months later, "Hearts broke across America." The 1985 write-up went on to report that Koko had received a new kitty and signed "My cat good." Psychologist Francine "Penny" Patterson, who began teaching Koko sign language in the 1970s, published the book Koko's Kitten in 1987.