Continuity mistake: When Samuel and Rebecca wake up in bed at Sean's house, they pull back the sheets to find Gail and Marty's little girl hidden under the sheets. When they pull them back she is seen facing the headboard and she screams when they do. The camera angle changes to a side view and as her parents walk into the room, she is seen now facing the door.
Continuity mistake: When Samuel and Rebecca first meet Dr. Kosevich, the first camera shot from the side of his desk shows he has 2 cups filled with pencils on the desk. The camera angle changes to a front view of his desk and we now see less pencils in both cups and pens have been added to them.
Continuity mistake: When Samuel and Rebbecca leave the Russian doctor's office after the examination table goes berserk, there is a pillow on the examination table that disappears when the doctor is seen from behind.