Revealing mistake: Sarah is reading her daughter a story about Snow White and the Seven Dwarves, but the cover of the book is Little Red Riding Hood.
Revealing mistake: The movie takes place over the course of several years, as large segments of time pass between scenes of Will and Jane meeting at the airport, and other encounters. Thus, it is rather jarring to notice that their twelve year old children, Ben and Claire, don't appear to age at all. Young adolescents usually change in appearance quite drastically as they mature.
Revealing mistake: Although the film is supposed to take place in New England, and there are constant references to how "Americans" do things, all of the license plates are from British Columbia.
Revealing mistake: When Darcy has caught up to Elizabeth in the end and they are kissing in the street with the police cars around them, if you look at the side of the cars, you can see that these Las Vegas, Nevada police officers are driving cars from the Provo, Utah police force (where the movie was primarily filmed). (01:36:50)
Revealing mistake: When Jessica Alba is getting up from the bed after sex, you can see the adhesive modesty patch covering her chest. (00:36:15)
Revealing mistake: The first night Ben brings Andie home, he starts the music on the CD player, but no CDs are spinning at all. Yet, the music still plays. He also changes the track mid-scene, and still no CD is spinning.
Revealing mistake: When Rolfe is walking down the hallway to Sally's apartment, there is an orb where the hallway is lighter colored and his legs seem to jump and undulate due to the special effect used to hide the fact that the actor is actually full-sized, walking on his knees.