When Raymond Shaw is talking with Ben in his election HQ office, he says, "...when we were in Kuwait..." but slurs the word to sound very much like "Korea". The original movie had the soldiers serving in (and abducted from) Korea.
Entertainment Weekly reported that Meryl Streep watched political talk shows to prepare for her role: "anything with Peggy Noonan, Karen Hughes... it's hard to get more hyperbolic than that." She didn't watch the original film, until after filming wrapped.
When Shaw's Secret Service Agent plants the rifle at the rally site for Marco, the spoken word piece "Kinky Sex Makes the World Go Round" by Dead Kennedys can be heard. The piece is about the U.S. "Secretary of War" calling Britain's Prime Minister suggesting "it's time to start another war", and suggesting that both countries give their soldiers, and young people who might be drafted, drugs to ensure compliance.
Before this movie's release, Paramount set up two official websites: one site with movie information, and one site that appeared to be a promotional tool for the fictional Manchurian Global Corporation depicted in the movie. The corporation website gave no indication of its connection to the movie, except a few references to its sponsorship of Dr. Atticus Noyle's Alzheimer's research. Similar advertisements for fictional medical procedures and clinics were also produced as parts of the advertising campaigns for Gattaca (1997), Godsend (2004), and Eternal Sunshine of the Spotless Mind (2004). Besides these films listed, Resident Evil: Apocalypse (2004) also has a advertising campaign featuring "Regenerator", a fictional product developed by the Umbrella Corporation.
The radio chatter audio near the end of the film, as Ben returns to the beach, is actually a recording of a Norfolk Southern train defect detector. If one listens carefully you can even hear it state, "NS (Norfolk Southern) detector milepost 79.8 one no defect." The actual detector likely reported 79.8 track one but the word track would spoil the illusion. It is interesting because these automatic reports only transmit two or three miles to inform the train crew of defects in their train. It is not likely they would be heard on a remote island.
In Richard Condon's novel, Mrs. Iselin's relationship with her son Raymond is explicitly incestuous, complete with a bed scene. For the 1962 adaptation, director John Frankenheimer and screenwriter George Axelrod reduced it to the less-than-motherly kiss that Mrs. Iselin plants on Raymond's lips. To appease the censors, Frankenheimer instructed Angela Lansbury to put her hand between their mouths and the camera to obscure what she was doing a little bit. In the 2004 remake, the camera cuts away before she kisses her son on the lips.
There is a brief shot of Worldwide Plaza (49th-50th Streets & 8th Avenue, New York City), the office complex on the site of the second (1925-1966) Madison Square Garden, where, in the original The Manchurian Candidate (1962), the assassination takes place (the inside and outside of the old Garden are shown in the original movie).