When David gets roughed up and rendered unconscious in the diner, he gets his suit all dirty from laying on the floor. In the next shot when he is in the jail, his suit is clean.
The back of Vincent's hand is covered in blood. When he is dropped off at the Lunch Counter, the blood disappears as he heads toward the door. The blood reappears when he enters the restaurant.
In the opening voice-over, narrator William Woodson states that Grady, Kansas is thirty miles from the geographical center of America. In Act IV, when asked by Ed Gidney why the aliens had chosen Grady for their experiment, David Vincent surmises that it's because Grady is about three miles from the center of the USA.
David Vincent is shot in the shoulder by Constable Gabbard after escaping from the police car. The wound bled through his shirt and his sport coat. Yet he never has the gun shot treated by a doctor or anyone else. When he comes out of the wash room at the lunch counter the cook asks him how his shoulder and he states that it is fine.
Butterflies are shown to eat meat. It is physically impossible for them to be able to do this, as they only have a proboscis.
Grady, Kansas is in a flat area, the tall hills shown in the background do not exist there. Additionally, the Eucalyptus and palm trees seen in the show do not grow in Kansas.
In one of the scenes when David is driving through town a sign "Chino Auto Parts" is seen. (Chino Auto Parts is in Chino, CA and not in Kansas).
Constable Gabbard fires his revolver noticeably before he is even finished aiming at Mr. Vincent.