What Makes a Scientist
Dr. Henry Jekyll, Dr. Victor Frankenstein, Doc Emmet Brown, Dr. Walter Bishop from Fringe, and characters like them throughout literature and film are categorized as "mad scientists." Sometimes it’s because their science is taboo or outside what society believes is even possible; sometimes they’re suspected of madness or some other kind of mental illness; sometimes it’s both. Why are these characters appealing to audiences, even if they’re not well-liked by the fictional societies they live in.
An analysis could include comparing them to real-life scientists like Galileo and Copernicus who were considered "kooks" but turned out to be right. Also, consider how driven these characters are to prove their theories, even pushing moral and societal boundaries – if they weren’t actually mad before, they can more easily be perceived that way by the end of their story.