CinemaBlend’s Adam Holmes interviews — really more at quoting a whole soundbite of — William Dafoe regarding the role of Green Goblin/Norman Osborn in Spider-Man (2002) film.
Norman Osborn had a definite “Dr. Jekyll moment” when he took performance enhancers in the lab and unleashed his power-hungry and violent darker consciousness, who becomes the villain in the film and later haunts the sequels.
The article uses the term “split personality” which may be a relief, since this character gains or unleashes an alter ego by way of a chemical cocktail, similar to Dr. Jekyll and Dr. David Banner (the Hulk) — this has no resemblance to real plurality. In both the article and the movie clip it is mentioned that Green Goblin is a murderer.