Leon is Cornelius' best friend at the science lab. He is usually a cheerful airhead (and nosy, like Stella) type of person. He always says silly things and stupid comments, and he never learns from his mistakes. Cornelius has a hard time dealing with him and often loses his cool with Leon. Leon is currently inventing a cookie-covered cat-shaped robot called "Princess Cookie". At some point in the story when he is knocked out.