Alexandra Day and her husband, Harold Darling, established the Green Tiger Press in 1970. In 1983, Harold and Sandra were visiting Zurich, Switzerland, when they came across a volume of old German picture sheets, one of which featured a poodle playing with a baby who was supposed to be taking a nap. This image provided the inspiration for Good Dog, Carl, which successfully began what would become an increasingly popular picture book series. The Darling's dog, a Rottweiler named Toby, was the model for the first book's main character. Since then, three other Darling Rottweilers have posed as Carl in the sequels. The Darlings now live in Seattle, Washington, where they have a ten-thousand-book library, primarily filled with illustrated children's books.