When Vickie is checking herself in the mirror before Craig comes to get her, she has on her cross necklace. Later in the morning, at the cafe, Craig gives her the cross necklace as a gift.
Mary Lou's hair changes length several times during her final scenes on the stage and in the prop room.
Before Mary Lou's dress ignites, the bottom is several inches above the floor. When it ignites, it is just touching the floor. Then when Mary Lou is engulfed in flames, the bottom of the dress goes back to being several inches above the floor.
On his way to pick up Vicki for school the streetlights are on. At that hour of the morning they would be off.
At the time this is set in: Jess would not have been allowed the Catholic Burial she is given, as they believe her death to be a suicide. Catholic burial was not allowed for suicides until recently.
Extremely obvious rubber pullover head mask on the transformation creature of Mary Lou towards the end of the movie. You can visibly see the rubber neck edging of the pullover mask stand off the actor's neck by at least two inches. This bad makeup job runs all the way across the front of the actors neck as the creature stands up on stage to full stance.
When the mother crashes through the glass of the front door of their house, the wig of the stuntman falls off when they hit the porch.
In the scene where Father Cooper and Bill Nordham are in Nordham's study talking about the return of Mary Lou Maloney, the boom mic is visible when Cooper is reading from his book.