The series is based on the popular New York Times bestselling book series collectively known as The Expanse,  written by Daniel Abraham and Ty Franck (under the pen name James S. A. Corey). Abraham and Franck will be show producers.
A tortoiseshell cat is a coat color where the cat is a molted brown cat with black, reddish, or orange patches. They can also have white paws. Tortoiseshell cats have unique genetics. The vast majority of tortoiseshell cats are female, because two X chromosomes are required to produce black, gold and orange coloring.
Calico Cats are not a specific breed of cat but it is pattern of colouring that gives the name. These cats are tri-coloured with patches of white, red or orange and black fur. A tortoiseshell cats are the calicos but with the colour pattern of orange and black fur mixed.