Continuity mistake: At the end of the movie the daughter hands Harry a stem of flowers. The flowers have small daisy like heads. However, when the shot changes to show Harry holding the stem, it is very different. There are less flowers on the stem and the petals are larger.
Continuity mistake: When they are putting Harry on top of the car his feet are pointing up, but when they are driving down the road Harry is now face down on top of the car.
Continuity mistake: It goes from night to day really quickly as Irene shows up.
Visible crew/equipment: When the family is escaping in Dr. Wrightwood's car with Harry, they leave the home after popping Lafleur's tires. There is a brief shot looking at George driving. The shadow of the camera rig is left screen.
Revealing mistake: When Harry screams through the windshield of a car you can see the actor's mouth and teeth inside of Harry's mouth.