The Danza: The three main characters share their names with their actors.
Enforced Method Acting: The actors were screened for their improvisational ability, and given a 35-page outline of the movie. All dialogue was improvised. The directors began rationing the actors' food to make them as hungry as their characters. They were not told when strange noises would be made, or when the tent would be attacked. Makes for some great acting.
Pay attention to Heather's screams at the end; according to the directors, she wasn't acting, and was.freaking out for real.
Executive Meddling: Artisan recut the film and re-shot certain scenes to add more "traditional" horror movie elements instead of the ambiguous flick the director was aiming at. Among other things they also changed the soundtrack to heavy metal and rock. Oh, and that "Book of Shadows" which appears nowhere in the film? Studio addition.
Franchise Killer: A trilogy was planned. The second film performed so badly that the third film was scrapped.