Uncle Fyodor
Six years old in the beginning and not much older afterwards, Uncle Fyodor is a
Wise Beyond Their Years boy whose decision to go to Prostokvashino rather than let his parents throw out his cat kicks off the plot.
- Bookworm: He's a very avid reader.
- Friend to All Living Things: He loves animals, especially cats, which leads to a quarrel with his mother in the first book. When he moves to Prostokvashino, people start bringing him injured animals and he cares for them.
- Honorary Uncle: For his Wise Beyond Their Years character, everyone calls him Uncle Fyodor rather the expected Russian pet name form "Fedya".
- Only Sane Man: He is the one to mediate the quarrels between Sharik and Matroskin.
Matroskin
Matroskin is a cat who taught himself to speak, mostly thanks to Professor Syomin, one of his previous owners.
Sharik
Sharik, like Matroskin, has belonged to Professor Syomin and gradually taught himself to talk.
Pechkin
Pechkin is the nosy village postman and the one to reveal Uncle Fyodor's whereabouts to his parents in the first book.
- Adaptational Nice Guy: His nosiness and bad temper are significantly toned down in Popov's animated adaptations.
Hvatayka
Uncle Fyodor's jackdaw whom he adopts when already in Prostokvashino.
Uncle Fyodor's parents
Dmitry and Rimma, Uncle Fyodor's parents. Rimma's dislike of pets is what leads to Uncle Fyodor leaving them in the first book.
- Foolish Husband, Responsible Wife: Dmitry is frequently a Cloudcuckoolander while Rimma is a lot stricter.
- Happily Married: Apart from occasional bumps on the road such as the misunderstanding in Winter in Prostokvashino, they are a very happy couple.
- My Beloved Smother: Rimma has shades of this in the first book, planning to hire a full-time nanny for Uncle Fyodor as soon as he comes back and unwilling to let him make his own decisions on anything. She gets better when she learns how well he's doing in Prostokvashino, and by the following books she is even comfortable leaving him in Matroskin's care.
Professor Syomin
A linguistics professor, former owner of Matroskin and Sharik.
- Good All Along: Downplayed, since he isn't believed to be evil, but in the early chapters of the first book, Matroskin and Sharik suspect he will take them away again. When he appears on-page, he says he has no such intentions.
- Speaks Fluent Animal: He studies animal languages and has published dictionaries of the languages of cats, dogs, and cows.
Katya
Professor Syomin's niece who makes her debut in
Uncle Fyodor's Girlfriend.
- Puppy Love: She and Uncle Fyodor form a mutual crush, much to the chagrin of Matroskin and Sharik.
- Remember the New Guy?: She appears midway through the franchise with no earlier indication of her existence.
Aunt Tamara
Uncle Fyodor's maternal aunt, a retired army colonel.
- Brawn Hilda: So fat that she needs a double bed to sleep, and a retired soldier.
- Chuck Cunningham Syndrome: Downplayed. In the end of Uncle Fyodor's Aunt, she is appointed the mayor of Prostokvashinsk, suggesting she'll stay in the region for at least a few years. However, in the following stories, she appears briefly or communicates with the main characters via letters at best, and is rarely ever brought up.
- Well-Intentioned Extremist: She is a perfectly well-meaning woman who wants the best for her nephew and his family and friends. It's just that her idea of the best is making everyone's life a torment with her The Spartan Way militarism.
