The Jellicles are a group of small, black-and-white cats who inhabit a whimsical, anthropomorphic world. They rest quietly during the day, washing behind their ears and drying between their toes in typical feline fashion. However, at night, they exhibit sophisticated, human-like behaviors by practicing formal folk dances under the moonlight. They are essentially creatures of privilege and leisure, dedicating their time to preparing for their grand midnight gatherings.

Old Deuteronomy is the oldest and wisest feline in the cats' social circle. He holds a respected, authoritative status among the younger animals. His name references a book in the Bible, giving him a patriarchal and venerable aura that commands reverence from the rest of the community.

Mr. Mistoffelees is a clever feline conjurer who brings a sense of magic to the cat society. His name serves as a pun on the demonic figure Mephistopheles and the phrase "mist fades off with ease." This wordplay directly describes his primary talent for disappearing smoothly into the background.