A day after the terrorist attacks on the USA of 11 September 2001, Roger Michell had the WTC towers digitally removed from the opening main title sequence in the film. In the DVD commentary, he admitted that it was a mistake to erase them and make it appear as if they did not exist. During the re-editing of the film, Michell reinserted them as a tribute.
The interior of the house that Doyle Gipson is seen in during the main title sequence was not a set. It's in fact the interior of a real house in Queens, New York which Roger Michell had found while scouting locations.