Alexandra Day is the author and illustrator of Good Dog, Carl and the rest of the beloved Carl books, including Carl Goes Shopping, Carl's Christmas, Carl's Birthday and Carl's Snowy Afternoon. The Darlings' own dog, a Rottweiler named Toby, was the original model for the main character of Good Dog, Carl. Since then, two other Darling Rottweilers have posed as Carl in the sequels: the late Arambarri, who was named for one of the Darlings' favorite jai alai players; and Zabala, who currently moonlights as an Our Best Friend therapy dog, visiting hospitals to cheer patients.