In the beginning of the film John and Detective O'Hara are driving. She suddenly gets really sick, so John stops the car so she can get out. She runs and then throws up. When she comes back to the car she trips on a log that was never there before.
Ivan Reitman put his son, Jason Reitman, and daughter, Catherine Reitman in the film. Jason is the boy making out with the girl during the fire, and Catherine is one of the third grade students.