Continuity mistake: When Kate enters the room with the cot at Brad's father's house, she unbuttons all three buttons and begins to open her coat. The shot then changes to Brad's face for some time. On the return shot of Kate, she's beginning to unbutton the coat all over again, starting with the first button. (00:18:25)
Factual error: When Brad and Kate are in the taxi on the way to the airport, they are shown crossing the Golden Gate Bridge. They supposedly live in the city of San Francisco itself, and therefore should be heading south to the airport. The Golden Gate Bridge is to the north, and is completely in the opposite direction, by about 18 miles.
Continuity mistake: At Brad's mom's house, after Brad and Kate are finished with their frustrating turn at the board game and Brad shuts down, saying our time is up, the hour glass is fully turned upright with all the sand in the top section. In fact, the sand doesn't even seem to be dripping into the bottom section.
Character mistake: During the Nativity play, Pastor Phil says, "Are we ready to see the result of the Immaculate Conception?" The term 'Immaculate Conception' refers to the conception of the Virgin Mary (conceived without Original Sin), not to the conception of Jesus. Furthermore, the Immaculate Conception is a dogma of the Catholic Church, and not something which a Protestant pastor like Phil would believe in.
Character mistake: They are hooking up Brad's father's satellite dish and he falls pulling the TV up to the roof. The cable is connected to the TV. The problem is all dish systems have a box that goes with them. The cable goes from the satellite to the box, then to the TV - not directly to the TV set.