Chiyo-chichi ("Chiyo-Dad" 「ちよ父」"Chiyo-chichi"), is a strange yellow to orange-colored cat like creature, who appears to Sakaki and Osaka in their dreams. He claims to be the father of Chiyo, he is quite easily angered and when so, he shakes violently while changing colors. He may be bullet-proof, a great baseball player, and/or Santa Claus. Osaka gives Chiyo a stuffed animal shaped like Chiyo-chichi on her birthday. In addition, he finds the color red discomforting, and is inconsistent about whether he really is a cat. In the English dub, he is known as the "Father Cat". His pupils are black in the anime, but in the color inserts from the manga they match his fur instead. In Sakaki's dream, he shows slight knowledge of himself not being a real cat, as he tells Sakaki to "find a real cat". However, when Sakaki mentions this to him in the anime, he grows angered and appears to remember nothing of this conversation. He also appears to have a dislike for tomatoes, as they are red, but he ensures Chiyo eats them, to keep up her health. He always has the same facial expression, even when upset (his pupils only get slightly smaller), and his mouth is never closed. The identities of Chiyo's real father (and mother for that matter) are unknown. It is mentioned that they are alive, but they are never seen or heard.
Year 1Chiyo-chichi appears for the first time in Sakaki's New Year's dream. Chiyo introduces him as an abandoned cat who needs help, and Sakaki takes care of him. Then Chiyo-chichi reveals that he is not really a cat, but Chiyo-chan's father, and thanks Sakaki for taking care of his daughter. He also tells Sakaki to find a real cat, but does not specify how she can do so.
Birthday partyChiyo-chan hosts a birthday party at her house when she turns eleven. Osaka gives her a plushie that looks exactly like Chiyo-chichi, which confuses and scares Sakaki. She tells the others that the cat is Chiyo-chan's father, but they do not seem to understand.
Year 2Sakaki dreams about Chiyo-chichi again when the new year begins. This time, she is invited to join him and his daughter for dinner. First, he asks Chiyo about what is popular at school these days. He is also fiercely insistent upon Chiyo eating her tomatoes, even though he doesn't dare eat them himself since they are red. He asks Sakaki to talk to him about her problems and she says she is troubled by the fact that she is so tall and that cats hate her. This information seems very intriguing to Chiyo-chichi, and he keeps asking her to make more confessions. He says he heard of how they made a hat shaped like the upper half of his face during the second cultural festival, and seems angry that they didn't ask him first. He gets even more wrathy when Sakaki tells him that if someone really did cut you right across the face like that, you would die.
Supplementary LessonsIn Supplementary Lessons, Sakaki thinks that if you put a photo under your pillow, you will dream about whatever's in the photo. Sakaki puts a photo of a cat under her pillow since she wants to dream about taking a walk with a kitty. When she falls asleep, Chiyo-chichi turns up in her dream and they take a walk in Nara together. Sakaki tells Chiyo-chichi that she finds him unique, which makes him upset because he hates uniqueness. Sakaki asks him what kind of college he thinks she should apply to, and he answers "keep moving forward, then turn left at the second corner".
Year 3During the girls' third year, many days off are spent studying at Chiyo-chan's house, and Osaka usually sleeps under the kotatsu using the Chiyo-chichi plushie as her pillow. Once when she does this, Chiyo-chichi shows up in her dream about studying in a classroom. He begins to speak English with her, since his daughter is going to America. Osaka tells him that she thinks he looks like Prime Minister Mori (Bill Clinton in the English dub of the anime). This insults Chiyo-chichi. Then Maya shows up. Chiyo-chichi asks him if he has a cat's tongue. Osaka says that she does, and then Chiyo-chichi tells her that he will yank out her tongue, after which Osaka wakes up. Osaka is confused about Chiyo-chichi mentioning his daughter's going to America afterwards, and when Sakaki explains that Chiyo-chichi is Chiyo's father, Osaka says that she gets it.