The story that Uncle Jack tells Nick of a Native American massacre was inspired by the horrific Bloody Island Massacre of the Pomo Tribe people, which occurred on May 15th, 1850 on an island called in the Pomo language, Bo-no-po-ti or Badon-napo-ti (Island Village), at the north end of Clear Lake, Lake County, California. It is said that up to 400 Pomos were slaughtered by U.S. Cavalry as punishment when they rebelled against local cattlemen who had been abusing the men as workers, and sexually abusing the women and young girls. One of the Pomo survivors of the massacre was a 6-year-old girl named Ni'ka, or Lucy Moore. She hid underwater and breathed through a tule reed. Her descendants formed the Lucy Moore Foundation to work for better relations between the Pomo and other residents of California. She was the inspiration for the shape-shifting Native American woman in the story - and happens to be played by an actress whose first name is also Lucy.
The character of Angie was inspired a bit by Norman Bates mother in Psycho, and her rising anger and resentment at Nick is linked to the reveal at the end of the movie. The decision to not show Angie on camera was at first about keeping the budget low, and because it was originally going to be a smaller role. Gualtiero Negrini was so impressed with Bettina Devin's performance that he then added a bigger last scene for her. He ultimately felt that keeping her character as a voice that is only heard over the phone made her presence more disturbing and ominous.
During the last weeks of post-production the Negrini family's beloved orange tabby, Thomas, had his life taken by a speeding hit-and-run driver. One day, while working on the night scene in the graveyard, Gualtiero Negrini was frustrated that the eyes on the Wolf (Ari) weren't looking right in the dark lighting. He decided to take a break and happened to glance at his favorite photo of Thomas that was leaning against the tin holding his ashes on a mantle. Immediately he noticed that Thomas' eyes had the exact intense, but soulful, expression he was looking for with the Wolf. He decided to use Thomas' eyes from that photo, and composited them onto the Wolf. The movie is dedicated to Thomas Negrini.
The story was inspired by a tale told for years in the same area where the movie was filmed.
The exterior of Uncle Jack's house was a three-wall set unit built in Lucerne Valley, California, and the interior was filmed in South Pasadena. During filming, the winds were so bad that the entire set piece was blown down twice. The small crew and a few actors scrambled to quickly prop it back up, paint over any scratches and resume filming.