Jimmy Choo, the shoe designer, was asked to make 63 different pairs of shoes for the film, all out of man-made materials (to be animal-friendly along the line of the line of non-animal cruelty, the line of the film). Reese Witherspoon asked to keep them all, along with all of the designer clothing she wore in the film.
During the opening scene, while looking at the scrapbook, one of the girls points to a photo of Elle with Congresswoman Rudd (Sally Field). She says, "Those are two kick-ass women. I like them, I really like them", a reference to Sally Field's acceptance speech at the 1985 Oscars.
The scenes on the steps of the U.S. Capitol were filmed at the Utah State Capitol. The scenes inside the Capitol were actually filmed at the Illinois State Capitol Building. Both were modeled after and look similar to the national Capitol. Many Salt Lake City and Springfield locals took parts as extras in the movie.
Interestingly enough; many dogs that worked for only one day on the "Million Dog March" scene were given a screen credit while Production Assistants, who had worked several months on the movie, did not.
The press junket for the film was held in London instead of Los Angeles because Reese Witherspoon, who was five months pregnant at the time, was shooting Vanity Fair (2004) there. MGM flew two-thirds of the junketeers to the city where they stayed at the Grosvenor House, a luxurious prewar hotel.
Up until Sing 2 (2020), this had been the only sequel film of Reese Witherspoon. After having had an unpleasant time doing this film, Witherspoon denied ever starring in a sequel again, thus other films of her's that had sequels either left out Witherspoon's character altogether, or they didn't happen under her respect.