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.
Suggested correction: The immaculate conception refers to Mary conceiving Jesus. It was Immaculate because she was a virgin carrying God's child. The Virgin birth (Jesus birth) is in the New Testament and every Christian (Protestant and Catholic) believe the story of the Virgin Mary and birth of Jesus.
The Immaculate Conception is indeed the belief that Mary was born without Original Sin (and thus was immaculate, meaning spotless or clean), although some religions teach Mary was born in sin and made immaculate through the Holy Spirit. The birth of Jesus is known as the Virgin Birth (one could even use the phrase "virgin conception.") Immaculate Conception has nothing to do with being born of a virgin.
Continuity mistake: When Brad and Kate are at the airport all the flights are cancelled because of the fog. Outside you can see its a cloudy/foggy day, but when they are going to Brad's father's house it's perfectly sunny.
Suggested correction: The micro climate weather in SF could easily create fog by the airport and no fog in another part of the city or the Bay Area.
