At the beginning of the movie, if you listen carefully to the tuba and tambourine zombies in the town bandstand, they are playing notes from "The Gonk", the mall music from George A. Romero's Dawn of the Dead (1978).
George A. Romero was so impressed with Simon Pegg and Edgar Wright's Shaun of the Dead (2004), that he asked them to appear in this, the fourth part of his "Dead" series, and they appear as the photo-booth zombies in the carnival and barroom sequence. They also feature prominently in the artwork for the Unrated Director's Cut.
The view of the zombies rising from out of the river is an homage to the classic scene from Herk Harvey's Carnival of Souls (1962), where the dead rise out of the Great Salt Lake before the dance sequence.
This movie's Pittsburgh premiere was at the Byham Theatre, which used to be called the Fulton Theatre. This theater, when it was still the Fulton, was the same theater where Night of the Living Dead (1968) premiered in 1968.
The opening credits includes a montage detailing the zombie outbreak leading up to the events of this film, with black and white footage and radio broadcasts depicting the infection's spread over the Earth. Some of the images come from George A. Romero's Night of the Living Dead (1968) portraying the beginning of the outbreak. Romero wanted to use more footage from the other two films of the series up to that point, Dawn of the Dead (1978), and Day of the Dead (1985), but was unable to due to complications with the rights of those films. This is because each of his zombie films have been produced by different studios. This can also be seen in the credits for Tom Savini's cameo in the film. He is the undead version of the character he portrayed in Dawn of the Dead (1978), named "Blades", but he could only be credited in this film as "Machete Zombie".
George A. Romero intended to make this film in his hometown of Pittsburgh, Pennsylvania. The story is set there, and it's where he made his other zombie films. However, the producers insisted on filming in Toronto, Ontario, in order to take advantage of Canadian tax incentives, creating a setting that retains Pittsburgh's geography, with physical locations of Toronto that have been altered.
This is the fourth film in George A. Romero's zombie series, which Romero says takes place after Night of the Living Dead (1968) with no specific time frame. The last zombie film he wrote and directed was Day of the Dead (1985).
Asia Argento (Slack) is the daughter of noted Italian horror filmmaker Dario Argento, who was the co-producer and co-composer of one of the previous entries in George A. Romero's zombie series, Dawn of the Dead (1978).
"Fiddler's Green" is a song about the place where cavalrymen go when they die, located "Halfway down the trail to Hell", and, in the end, advocates suicide by pistol when death is certain, and the hostiles are closing in. "Fiddler's Green" possibly originated in England at least to the nineteenth century, and is still sung today. The song speaks of a place where fisherman go, if they don't go to Hell. It found its way to the U.S. with the help of Cornish settlers. The fictional place of Fiddler's Green is also the final resting place for pirates.
Susan Wloszczyna, a reporter for USA Today, appeared as one of the zombies. She was there interviewing her fellow zombies, as well as the director. She spent nearly an hour and forty-five minutes in the make-up chair.
The first trailer for this film used clips not just from Night of the Living Dead (1968), but also from Dawn of the Dead (1978), and Day of the Dead (1985), Although Night is in the public domain, both Dawn and Day are owned by separate companies, neither of which had given permission for the use of footage in the trailer. To avoid legal troubles, this trailer was quickly pulled from distribution, and hasn't been officially shown since.
The rifle carried by Charlie (Robert Joy) is an M-1 Carbine, a weapon developed during World War II. It was noted for its superb accuracy (for a carbine), and also hated by the Marines for its puny stopping power.
Dennis Hopper and Robert Joy previously appeared in Waterworld (1995). In that movie, Hopper's character licks his thumb and touches his rifle's sight before taking a shot. This is also a signature quirk of Charlie (Robert Joy) in this movie.
Alan Van Sprang and Shawn Roberts are the only two actors to carry over to another "Dead" movie by playing different characters. Alan Van Sprang was in Land of the Dead (2005) as a soldier named Brubaker, who died and became a zombie, and he was Sarge in Diary of the Dead (2007), and Survival of the Dead (2009). Whereas Shawn Roberts played a rookie called Mike, in Land of the Dead (2005), and one of the students named "Tony Ravello" in Diary of the Dead (2007).
Movie theaters showing this film in the U.S. were given a replacement track for the typical music and commercials usually heard playing over still images of advertisements before a movie starts. This track consisted of sound bites of music and lines from Night of the Living Dead (1968), and Day of the Dead (1985), along with an advertisement for then upcoming airings of Day of the Dead (1978) on a pay-per-view network.
The trivia item below may give away important plot points.
In the scene where the zombies get into the city, the soldier playing cards, who has his head pulled off, his camouflage uniform says "Rickles" in the name area. Rickles was the name of one of the soldiers from Day of the Dead (1985).