The Exorcist Kept The Actors On Their Toes
Being on the set of The Exorcist was essentially torture for everyone involved. Director William Friedkin was ruthless to the entire cast in order to make the film seem as real as possible. He would make the set so cold in order to make the cast shake as though in fear to the point that they could see their breath or fire guns randomly to keep everyone on edge.
In one instance, during the iconic vomiting scene, actor Jason Miller who played the priest knew that there was going to be a little vomit involved and was told it was going to be aimed at his chest. Instead, he got a face-full of green pea soup since Friedkin knew that he hated the stuff. So his disgust, fear, and overall reaction were as real as it gets.