Mejiro McQueen is a petite horse girl standing 159 cm tall, distinguished by her lavender hair, violet eyes, and a signature teal ribbon adorning her right ear. As a scion of the prestigious Mejiro racing family, she embodies a dignified and graceful demeanor reflective of her lineage. Her driving ambition is victory in the Spring Tenno-Sho, a race deeply significant to her family, and she trains relentlessly to honor this legacy. Specializing in long-distance events, she resides in Ritto Dorm at Tracen Academy with her roommate Ikuno Dictus. Her personality merges aristocratic poise with an underlying gullibility and hidden sensitivity; though reserved at first, she reveals genuine care for others. She adheres to a strict performance diet yet secretly battles a sweet tooth. Daily rituals include precise body temperature monitoring before races—a childhood habit—and savoring afternoon tea poured with the idiosyncrasy of adding milk before the tea itself. Private quirks surface in motivational sleep-exclamations. Her interests encompass avid baseball fandom, influenced by Mejiro Ryan and favoring the Hanshin Tigers/Yutaka Take, plus collecting B-movie brochures as a tribute to her namesake, actor Steve McQueen. Relationships define her: she shares a close bond of friendship and rivalry with Tokai Teio, endures frequent pranks from Gold Ship despite their mutual respect, and actively participates in Team Spica. This includes supporting teammates during events like the relay race aimed at reconciling Biwa Hayahide, Narita Taishin, and Winning Ticket. In the "Uma Musume: Pretty Derby - BNW no Chikai" OVA, she contributes to Team Spica's relay race efforts, assisting in clarifying misunderstandings during recruitment, such as Special Week's approach to Winning Ticket. Her role reinforces her supportive nature within the team. Her character draws from a real racehorse dominant in early 1990s long-distance events, achieving consecutive Spring Tenno-Sho wins and cementing a three-generation legacy in the race. This history shapes her narrative focus on family honor and racing excellence. Design elements like her black-and-white race outfit and teal socks reference the real horse's coat and jockey silks. Her established persona and background remain consistent throughout her appearances.