Continuity mistake: In the part where Meg is asking Brian about God, and Brian answers he is an atheist, the camera pans out quickly, and we see an entrance to the kitchen with an air vent above it. Eventually the family discussion with Brian continues, and you see that the air vent is now gone.
Continuity mistake: While Meg is at the kitchen table telling the family about her new life with God, you will notice that Brian is sitting to the right of her. As she starts to ask that everyone hold hands, take notice that Brian is not in that chair and that Brian's plate and utensils are moved closer to Meg. As the shot pans out, Brian is back in that chair.