A small, cartoonish black and white mouse that first made its appearance in the animation Kanaka no Yume Mahou. In recent years, it has served as the mascot of Kyoto Animation along with Gaa-chan.
Kyoto Animation released a special animated feature starring Baja Mouse titled Baja no Studio ("Baja's Studio") on a Blu-ray disc package containing tickets for the studio's 2017 fan event.