Goofs

When "Ken" and "Daphne" have sex in the bathroom, she rips off his shirt and the buttons visibly fly off, but when they emerge, the shirt is nicely buttoned.

Kate's hair is completely different when she leaves the bathroom at her mother's house.

When the family is playing Taboo at Brad's mother's house, the Taboo Timer isn't visible until Brad says "Our time is up," at which point the hourglass timer appears to have just started.

When Brad and Kate are talking outside the front door when he returns, her makeup keeps switching: eyeliner/no undereye circles and reddish lipstick to no eyeliner/undereye circles/pinkish lipstick and back again.

When Kate is in the bathroom at her mother's house, the pregnancy test she sees in her sister's bag disappears and reappears a few times.

Breast pumps need a tight seal in order to work; they would not stick to a knitted sweater as depicted.

During the Taboo game, Denver answers "What is the capital of China?" with "Hong Kong". This is part of the joke. Denver and his wife, who obviously have little education, think that Hong Kong is the capital of China. The point of the game was for Denver to guess that "Hong Kong" was the answer on the card, which he did. The point of the scene was to demonstrate how well they knew each other and how poorly Kate and Brad knew each other. The fact that Denver got "Hong Kong" from "What is the capital of China?" helped to make that scene funny.

Brad refers to Burma as an Asian "island nation"; its southern border is its only coastal border, so it's not an island. (He's lying to his parents about going there, a lie so ill-conceived that he doesn't even know this basic fact.)

Pastor Phil calls Brad by name to participate in the nativity play without having been introduced; a deleted scene shows the introduction, but the final cut doesn't.

While Kate and Brad are arguing in the car on the way to her father's, there is an obvious reshoot because at some points she's wearing a wig and in the next shot she has her normal hair, then back to the wig, throughout the scene.

When Kate and Brad are in a heated conversation in the car, in the background the car has made an obvious turn, but Brad doesn't move the steering wheel once.

A news crew is shown doing a live report with a wireless video camera, a technology that wasn't in use in 2008, when the film takes place.

Kate and Brad's taxi is seen going over the Golden Gate Bridge on the way to the San Francisco Airport. Taking the Golden Gate Bridge actually takes them away from the airport.

Susan prepares a Spam casserole in Howard's kitchen using Hellman's Mayonnaise, which isn't available in California. West of the Rockies it's sold as Best Foods, although both are made by the same company with the same recipe.

When they are leaving for the airport to head to Fiji, they start in downtown SF and head North to cross the Golden Gate Bridge. The airport is south of the city.

When the baby spits on Kate at her mother's house, she claims to have no change of clothes. But she has an entire suitcase full of clothes in the car outside, as she was supposed to go to Fiji.

No reporter, especially one for a major network in a big city like San Francisco, would simply go up to random people and begin interviewing them on live television. First, as shown in the film, the interviewee can freeze up not knowing how to respond. Second, as implied by the film, there are privacy concerns. In reality, the reporter, or more likely someone from the crew, would ask the person first and get the necessary legal documents signed first giving the person a chance to think of their response.

When Brad and Kate are playing backgammon on the sofa he shows her where to move her pieces by moving one clockwise and one counterclockwise. In backgammon a player's pieces move in one direction.

At around 49 mins., Pastor Phil, beginning the church Nativity Pageant by asking "Are we ready to see the results of that immaculate conception?" implying that the "results" are the birth of Jesus. The title "Immaculate Conception" refers not to Jesus but to his mother, the Virgin Mary, without Original Sin (thus, Immaculate) in the womb of her mother, Saint Anne. Mixing up these two events is a common misconception.