Shimajirō Shimano is an anthropomorphic Siberian tiger cub with yellow fur marked by distinctive black stripes. He features round ears showcasing white inner sections, a pair of whiskers, and a brown nose. His wardrobe has evolved: he initially wore a green sweater under blue overalls with red buttons, paired with sky blue shoes over white socks. He later adopted a red sweatshirt featuring a white kangaroo pocket accented by red stripes, dark blue shorts, and brown shoes with white socks. He currently sports a red long-sleeved shirt with a left chest pocket, denim knee-length shorts, and dodger blue sneakers over white socks. Seasonal variations include a white t-shirt with red sleeve patches and denim shorts for summer, occasionally topped with an olive safari hat.

Personality-wise, Shimajirō bursts with bright energy and pronounced curiosity. He tackles activities enthusiastically, though intermittent selfish tendencies sometimes draw peer criticism, leading to valuable learning experiences that shape him into a kind individual who values life lessons. He demonstrates strong supportive instincts towards friends and his younger sister, Hana, though stubbornness and mischievous behavior periodically surface. He specifically enjoys donuts, dinosaurs, soccer, and exploration, while disliking bell peppers. Fears include thunder and ghosts. His active imagination fuels vivid daydreams, and physical tells like uncontrollable eyebrow twitching occur when he attempts deception.

Residing on Challenge Island, he navigates typical preschooler experiences in a kindergarten setting. Daily activities involve learning practical skills like toilet use, resolving conflicts, assisting others, and participating in group endeavors. His family consists of parents Shimataro and Sakura, and younger sister Hana. Key peer relationships include Mimirin Midorihara (a rabbit whose initial meeting caused Shimajirō shyness), Ramurin Makiba, Torippii Sorano (a parrot sharing a notably close bond with him), Nyakkii Momoyama, Kirinta Kusano, Pontaro, and recurring rival Tamasaburo Hyodo. His name reflects his traits: "Shima" (stripes), "ji" (next), "ro" (son), and "Shimano" combines "shima" (stripes) and "no" (field).

In the film "Eiga Shimajirō Miracle-jima no Nanairo Carnation," Shimajirō embarks on an adventure to Miracle Island. He collaborates with friends to help a boy named Miller recover stolen rainbow carnations – wish-granting flowers taken by an antagonistic magician. This narrative reinforces his established traits of curiosity, helpfulness, and collaborative problem-solving within the group dynamic.