Lisa and Lottie (original German title: Das doppelte Lottchen, "The Double Lottie") (published since 2014 in the United Kingdom and Australia as The Parent Trap) is a 1949 German novel by Erich Kästner, about twin girls separated in infancy who meet at summer camp. The book originally started out during World War II as an aborted movie scenario. In 1942, when for a brief time Kästner was allowed by the Nazi authorities to work as a screenwriter, he proposed it to Josef von Báky, under the title The Great Secret, but the Nazis once again forbade him to work. After the war, Kästner worked the idea into the highly successful book. Subsequently, it has been adapted into film many times, most notably Disney's 1961 film The Parent Trap starring Hayley Mills, the subsequent film series, and their various translations.