Shippona, a small cat owned by the Kagami family and specifically belonging to the main protagonist, debuted in the first 1969 anime adaptation before appearing in later media iterations. The name "Shippona" originates from "ship owner," reflecting how Akko's father discovered the cat aboard a ship he worked on and subsequently adopted it. Across adaptations, Shippona is consistently depicted with black fur and distinctive white paws.

Narratively, Shippona primarily functions as a companion animal but occasionally becomes involved in plotlines where the protagonist uses her transformation abilities to assume Shippona's form. These instances typically involve resolving feline-related conflicts or gathering information from an animal perspective. Shippona also shares recurring interactions with Dora, a larger cat owned by Taisho and Shosho, with some adaptations implying romantic interest between the two cats.

Shippona's presence varies significantly across different versions of the story. The character was incorporated into manga tie-ins created alongside the first anime and later became a recurring figure in the Nakayoshi manga run. However, in the 1998 anime adaptation, Shippona appears only in early cameos before being phased out. In the web manga "Himitsu no Akko-chan μ," Shippona makes a brief cameo in initial chapters but does not feature in subsequent stories.

A significant plot involving Shippona occurs in the 1988 anime adaptation, where the protagonist's accidental revelation of her secret transformation ability jeopardizes Shippona's existence, forcing the protagonist to undertake corrective measures. Beyond this and the transformation plotlines, Shippona's role remains consistently that of a household pet, exhibiting no notable character development or personality traits beyond typical feline behavior.