Early in the film, it is established that the continent is undergoing an unprecedented heatwave. Throughout the movie, though, people can be observed wearing coats, stocking caps, scarves, and long-sleeved shirts.
Jack Addison throws the car into reverse, yet goes forward, and vice versa.
Jack Addison makes a call from a pay phone without inserting any change.
When a stool is thrown through a glass door, you can see the glass shatter before the stool gets anywhere near the door.
At the end of the movie, the alien Burke (Larry Day) tells Jack Addision (Patrick Muldoon) "no one will believe you" while standing in front of a HUGE hole in the ground where a nuclear power plant had just imploded (significant proof of the "truth").
Jack notices Bridgette has an engagement ring (on the wrong finger) and remarks that it must not have worked out. Bridgette states that she missed her wedding rehearsal working on a story. She continued to say that her fiancé saw it as a sign of things to come, meaning that this kind of thing would continue with her. Jack responds, "Well, his loss." Actually, not. She was the one in the wrong, so it was her loss.
Jack knew nothing about the other guy for him to say that.