The most difficult part of the writing was determining the story's goal, who the villain was and their goal, why ghosts were manifesting, and how a towering Marshmallow Man appeared. The Marshmallow Man was one of many elaborate creatures in Aykroyd's initial treatment, originally intended to emerge from the East River only twenty minutes into the film. It stood out to Reitman but concerned him because of the relatively realistic tone they were taking. While this process was occurring, Reitman was searching for a special effects studio for the film, eventually recruiting Richard Edlund in the same two-week span.