Mimirin Midorihara, also known as Mimi-Lynne in English adaptations, serves as a central character in the Shimajiro franchise. This young anthropomorphic white rabbit features pink inner ears, black ear tips, a distinctive forehead tuft of hair, a pink nose, and a visible buck tooth. Her appearance evolves throughout the series: early seasons depict her with a reddish-pink flower-shaped hair clip, a pastel yellow sweater, and a red overall dress, while later iterations like *Shimajiro: A World of Wow* show her wearing a pink ribbon, a grey polka-dot dress, a pink cardigan, and blue striped socks.

She lives as the only child in the Midorihara family, who run Flower Shop Midorihara. This status became more pronounced following the departure of her close childhood friend, Ramurin Makiba, from Challenge Island, leaving Mimirin without siblings among the main cast. Her personality blends gentleness, naivety, and liveliness with occasional moments of being spoiled, clumsy, and emotionally sensitive, sometimes leading to tears if her opinions are ignored. Nevertheless, she displays bravery in making friends and exhibits diligence when facing challenges.

Mimirin holds specific preferences and fears: she favors strawberry shortcake, dolls, flowers, and running—excelling as the fastest runner among her peers. Conversely, she dislikes carrots despite her rabbit identity and harbors fears of snakes, caterpillars, and insects. Her social circle includes Shimajiro Shimano, Torippii Sorano, Nyakkii Momoyama, and kindergarten classmates Marurin Sasaki and Kikko Hayashida. Her bond with Ramurin was especially strong; before Ramurin moved to France, she gifted Mimirin a pink ribbon, which Mimirin adopted as her signature hair accessory.

Her name carries meaning: "Midorihara" (緑原) translates to "green fields," while "Mimirin" (みみりん) combines "ears" (耳) and "dignified" (凛). Additional background notes include her October 10th birthday, placing her under the Libra zodiac sign, and a blood type of B.