After Death: The first movie made by a dead person.
To promote the Puerto Rico Horror Film Fest, Badillo Saatchi & Saatchi contacted a medium and held a real séance. They channeled the spirit of María Mercé, who narrated a story which was then taken to the screen by Salado and Director Nico Lacouzzi.
This is the case study. Seance or not, I'll bet the film was quite scary.