Character mistake: Just after the shootout between the robbers and the armored truck drivers at the dip in the road, the teacher that is with the robbers pumps the shotgun about 3 times, without firing a shot after they crossed the water. This would just waste a perfectly good cartridge, since they hadn't been shot yet.
Character mistake: At the beginning of the movie, Marnie states that she is 13 years old. When Grandma Aggie comes to visit, she tells Mom that it is Marnie's 13th Halloween. Since everyone celebrates their first Halloween before they turn one, if Marnie is 13 the events of this movie would occur on her 14th Halloween, meaning her powers would have faded by now.
Character mistake: At the radio store a sign shown to Jack when he asks if they take personal checks is misspelled. It says "personnal." (00:58:55)
Character mistake: The banner of the fundraiser event for the Gotham upper class says "Childrens Hospital", no apostrophe. (00:11:55)
Character mistake: At the meeting in Washington the general says nothing more frightening than a soldier with his M16A1, but they were using M16A2s.