Ellen

Ellen is not ZUN's original character but a parody of one of the heroines of Hatarakimono (はたらきもの, lit. "Hard Worker"), a manga by Izumi Takemoto, full name Ellen Fuwafuwaatama (fluffy-head) Aureus (エレン・ふわふわ頭・オーレウス). In her ending, when she wants her new store's name to be "Fuwafuwa Ellen's Magic Shop", in reference to this. Sokrates is also based on this manga (ZUN notes that Ellen's clothing style and the "age" where cats were pets don't really match up, so the cat should probably be named "Archimedes" instead).