Revealing mistake: When Chelsea is on the roof of the house and Kathy joins her, Kathy's hair is blowing in the wind, while Chelsea's stays perfectly still, the water in the lake is also perfectly still. Obviously the director had the actors do the scenes separately until we see them both together in which case both characters hair is blowing around. (01:27:40 - 02:00:00)
Revealing mistake: Ryan Reynolds is wearing red-eye contacts. You can see the whites of his eyes around the red circle of the contacts in several scenes - most noticeably, right after the home movie he's watching down in the basement melts.
Suggested correction: Not a mistake. Ryan Reynolds actually had bloodshot eyes from being awake for nearly two days of filming. He stated it in an interview for the movie.
Revealing mistake: Towards the end, when the family is getting away from the house in their boat, you can see that the motor is a covered camera. It is too high out of the water to be a real motor and when the shot is not from behind the boat you can easily see the "motor" moving left and right while the boat is still.
