Continuity mistake: When the Red Dust is spread, there is a brief shot of some California citizens watching, and we see the Bernsteins among them. But the actress at George Mofogen/Mr. Bernstein's side is not Bonnie Bartlett, who played Mrs. Bernstein in the first two episodes.
Factual error: When the world celebrates the Visitors' flight, there are scenes of joyous people from all around the world. Curiously, in each of these scenes it is daytime - even in Italy, China, and India, where it would be either night or dawn, given that L.A. time of the attacks is between 11 and 12 AM.
Revealing mistake: When Julie is almost converted, a fake Donovan bursts in and starts firing a blaster rifle. Look closely at the first shot: the rifle is held way too high, so the shot should have gone into the ceiling; yet the blast goes straight forward.
Continuity mistake: When Julie and Robert infiltrate the hospital using the forged passes, the pass is shown twice as it is inserted into the reader. In the first shot, it slides in down whole, but the reader is still buzzing. In the second, the card starts sliding in again.
Continuity mistake: When the spaceship is hovering overhead, we see various shots of the Maxwell family and others. In one shot we see the family from behind with a person in blue. We then jump to a shot from the front with that person not in picture. We then go to another behind shot and see the same person hurriedly moving into shot. (00:10:20)martinharper