Best horror movie mistakes of 1980
Revealing mistake: During the scene in which Lou forces himself on Kim in the lunchroom, donning a black ski mask, Kim's brother Alex jumps up to his sister's defense. Just before Alex throws his first punch, Kim screams "Michael," referring to the actor's real name Michael Tough. Kim then correctly screams "Alex," the name of the character he was playing in the film.
Continuity mistake: When John is in his Manhattan apartment reminiscing, we see his daughter throw a ball at him. If you take a close look at the ball, you will see how beat up it is. However, when the ball is falling down the stairs in his rented house for the first time, it has become new and shiny.