Polygraph Operator: I'm going to ask you a series of control questions. Are you currently in a seated position?
Polygraph Operator: Are you human?
Klaatu: My body is.
Polygraph Operator: Do you feel pain?
Klaatu: My body does.
Polygraph Operator: Are you aware of an impending attack on the planet earth?
Klaatu: You should let me go.
As Klaatu is walking down the train platform at Newark Penn Station, in the background you can see signs that say "VIA". VIA is the national railway of Canada and does not have a presence in New Jersey. This scene was filmed in Canada, as evidenced by the signs on the platform and the 1950s style streamlined passenger cars on the track. Neither Amtrak nor NJ Transit uses those type of cars in their trains.
When Klaatu is shown on the tv as an escaped convict, the phone number shown to call to report him is not the usual 1-800-555 number, rather it is 1-800-472-0391 which is the Alaska Weather Information Hotline.