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.
Five years ago, I wrote a post titled Tortitude: The Unique Personality of Tortoiseshell Cats. The post describes some of the unique traits that many of these beautifully colored cats seem to share: they tend to be strong-willed, a bit hot-tempered, and they can be very possessive of their human.