Shimajirō Shimano is an anthropomorphic Siberian tiger cub sporting yellow fur marked by distinctive black stripes across his head, back, arms, legs, and tail. His features include a white muzzle, round ears with white inner sections, four black whiskers, and a brown nose. His wardrobe has evolved: he first appeared in a green sweater beneath blue overalls featuring red buttons, later switched to a red sweatshirt paired with dark blue shorts, and currently favors a red long-sleeved shirt with denim shorts and blue sneakers. Seasonal outfits incorporate lighter shirts and shorts for summer, while accessories like hats vary by story.

He is the son of mailman Shimataro and Sakura Shimano, and the older brother of Hannah (Hana). His family lives on Challenge Island, a fictional setting populated by anthropomorphic animals. Born on May 5th, coinciding with Japan's Children's Day, his blood type is O. His name reflects his tiger nature: "Shimano" (縞野) blends "stripes" and "field," and "Shimajirō" (しまじろう) signifies "striped son."

Personality-wise, Shimajirō exhibits a bright, energetic curiosity, brimming with enthusiasm for exploration, soccer, dinosaurs, insects, and donuts. He harbors fears of thunderstorms and ghost stories, and dislikes green peppers. Generally kind and supportive towards friends and family, he can occasionally act selfishly or stubbornly, leading to conflicts that teach him moral lessons. A notable tell involves uncontrollable eyebrow twitching when lying, though he eventually develops workarounds. He shares close bonds with characters like Mimirin Midorihara (a rabbit) and Torippii Sorano (a parrot), while maintaining a rivalry with Tamasaburo Hyodo. His social interactions frequently involve collaborative problem-solving.

Key experiences include cross-dressing as "Shima-Lynne" to humor his sister's wish for an older sibling—a disguise reused in multiple episodes for comedic or situational effect. He also participates in community activities like fire safety drills and traffic education OVAs. In the movie *Shimajirō to Kirakira Ōkoku no Ōji-sama*, he joins a quest to save the Glittering Kingdom with friends, answering Prince Pearl's distress call about vanishing birdmen, reinforcing his perseverance and teamwork within his established role.

His background involves attending Challenge Kindergarten, where he learns daily skills such as apology, empathy, and practical tasks like toilet training or plant care. Storylines emphasize age-appropriate challenges including making friends, sharing, and overcoming fears. His core growth centers on translating curiosity into learned virtues through episodic experiences across all media.