Reality Subtext: In the original cut of the film, there was a homeless woman living in the hospital. The crew never encounter her, just get hints of her presence. In test screenings, the audience confused this woman with another character, so she was cut from the film. However, many of the hints remain (some of them devoid of a good explanation, as the creators point out in the commentary track). These are now hints of something cut from the film, rather than merely unseen by the protagonists.
What Could Have Been: An original subplot for the film involved a homeless woman living in the place who kills Gordon after witnessing the murders. It was removed after test audiences found it too distracting from the main story, but wide shots that are supposed to be her seeing the murders are still left in the movie.