Continuity mistake: When the law enforcement officer arrives, there is a tight close up on the handle of his .38 revolver. When one of the aliens scans his body, an image of a .45 1911 appears instead.
Continuity mistake: When Sparks had just finished building the Lego model in Hannah's room to show what the machine was, Tom was saying that Sparks was different and Sparks gave him a big dark green Lego. But before he gave it to Tom, it was light green.