In an interview, director Paul W.S. Anderson said that Arnold Schwarzenegger offered to reprise his role as Dutch Schaeffer (from Predator (1987)) at the end of this movie as a cameo, but only if he lost the election for California governor.
The Antarctic setting on Bouvet Island is based on the unexplained "Vela Incident" of September 22, 1979, where a satellite recorded a flash of light near the island. It was first speculated to have been a man made nuclear explosion or a natural event such as a meteor strike, but this has never been resolved.
(at around 1h 6 mins) When Lex asks Sebastian how to say "scared shitless" in Italian, he replies "Non vedo l'ora di uscire da questa piramide con te, perché mi sto cagando addosso." Translated, this literally means "I can't wait to get out of this pyramid with you, because I'm shitting myself."
While this film languished in so-called "development hell" for years, 20th-Century Fox considered producing a fifth film in the "Alien" franchise instead. James Cameron, who wrote and directed Aliens (1986), had written a script and even approached Sigourney Weaver to star and Ridley Scott to direct, both of whom expressed interest. When the studio decided to use the Alien/Predator crossover story instead, Cameron, Weaver and Scott all distanced themselves from the project, and later, declared they would never work on either franchise again. Several years later, Ridley Scott ended up reworking his pitch into his Alien prequel Prometheus (2012).
Paul W.S. Anderson rewarded hardcore Alien and Predator fans by scattering references to the individual franchises within his film. For instance, the opening shot of the movie appears to be a silhouette of the Alien Queen from Aliens (1986), before being completely revealed as a Weyland Satellite.
The character played by Lance Henriksen, Charles Bishop Weyland, is a co-founder of the Weyland Yutani Corporation. This is "the company" referred to in the earlier "Alien" movies. He is the "ancestor" of the Bishop Android from Aliens (1986) and Alien 3 (1992), who were also played by Henriksen. In his office on the ship, he does the same hand trick as the Android in "Aliens."
The animatronic Queen was controlled by a motion-control rig which could save her movements digitally. So, if the Queen made a nice looking move in rehearsal, the move could be replayed verbatim in front of the camera.
The character of Verheiden was named after comic book writer Mark Verheiden, creator of the first Alien vs Predator comic series and the first story involving both species. Contrary to popular belief, the comic was released prior to the infamous shot of the alien "skull" in Predator 2 (1990).
(at around 13 mins) At the beginning of the film, the readout of the Predator ship is shown reflected in the visor of the predator mask, just as in Alien (1979) the readouts of the Nostromo were reflected on the space helmets.
According to director Paul W.S. Anderson, if they'd filmed in Hollywood, the sets would have cost them $20 million. In Prague, they only cost $2 million, an important factor in keeping the film's budget down below $50 million.
The green glow stick dropped down the shaft contains the same fluorescent liquid used by the effects departments of all the Predator movies as the Predators' blood. According to Predator (1987) director John McTiernan, they stumbled on the effect after unconvincing attempts to make the blood look orange forced the crew to look for alternatives.
(at around 27 mins) The shot taken from inside the pyramid of the team approaching the top with their flashlights references the shot in Alien (1979) of the Nostromo's expedition team walking up to the entrance of the derelict.
At one stage both Peter Weller and Gary Busey were approached to do a cameo as John Yutani, the other founder of the infamous "Weyland-Yutani" Company from the "Alien" films, but Yutani was written out of the script. The character was later used in the sequel, Aliens vs. Predator: Requiem (2007), this time as a female.
(at around 18 mins) When one of the explorers is searching the whaling compound and walks past a door to a building, there is a shot from within the building in which the red light from the guy's flare comes through the crack in the door to form a flat vertical beam that's picked up by the dust/snow from inside the room, just like the blue-green scanner from the salvage scene at the beginning of Aliens (1986).
The Alien vs. Predator story crossed over virtually all forms of media before becoming a feature film. There was a successful comic book series, toy line, multiple video games, soundtrack (of the PC game) and even a trading card series.
The scene in which Weyland's team discovers the sacrificial chamber inside the pyramid was originally longer than seen in the theatrical cut. After Rousseau and Thomas discuss the hole in the corpse's chest, Sebastian finds a calcified facehugger. Lex and Sebastian then theorize as to what the creature's origin could be. The scene was restored in the movie's unrated (extended) cut.
(at around 2 mins) At the beginning of the film, the technician in the satellite control station has a "drinking" bird among the Tweety Pie dolls. These are the same birds that were seen on the dining room table in Alien (1979) and the abandoned prison canteen at the end of Alien 3 (1992).
There's a shot where Lex pulls herself up a cliff. It's filmed exactly like the shot in Alien (1979) where Ripley (Sigourney Weaver) does the same, looking for the Alien, and in Aliens (1986), when Ripley pulls herself out of the airlock at the end. In both shots the characters are sweating heavily and one of their hands in front of their faces can be seen.
This was a project that had floated around for about 10 years. It was only when director Paul W.S. Anderson did his verbal pitch to the suits at 20th Century Fox that anyone showed any real interest. So much so, in fact, that they greenlit the film immediately.
20th Century Fox wanted Roland Emmerich to direct the film back in the late 1990's, due to the box office success of Independence Day (1996), but Emmerich turned down the offer, choosing to work on other projects.
Screenwriter Peter Briggs wrote his original spec script for "Alien vs Predator" in 1991. The script sold overnight and made him the subject of numerous magazine and book "success story" articles. His version went adrift following studio politics in the wake of executive Joe Roth's departure from 20th Century Fox.
Around the time of the film's release, it was reported that at a special industry screening, director Paul W.S. Anderson had said that the film was always planned as an R-rated movie and shot that way, but only three weeks prior to release the studio changed that by severely cutting the film for a lower PG-13 rating. This account has been heavily disputed by original "AvP" writer Peter Briggs. It was later revealed that this "press-screening" never actually took place, and was only an Internet rumor started by fans. Anderson has said in interviews that the film seen in theaters is the version he intended audiences to see. However, to appease the fans, an unrated version with added scenes and gore was released later.
On the official poster for the movie, with the Predator in the lower right corner and the alien in the upper left, drooling; the raised black parts of the alien's jaw, along with the opening in its mouth, spell out the letters AVP in an organic version of the font used for the movie's title.
Screenwriter Shane Salerno was the last writer and "closer" on AVP: Alien vs. Predator (2004). He worked on the film for 15 months, including prior to production, through filming in Prague and all the way through post production without receiving the co-screenplay by credit that 20th Century Fox recommended him for to the WGA. Shane has a co-screenplay credit on the novelization of the film, dozens of magazine articles, and many of the original theatre posters.
At one point, David Twohy was once approached by Fox Studios back in May 2000 about his availability to write and direct the film, but turned down the offer due to scheduling conflicts. Twohy had once worked on several unused story treatments for Alien 3 (1992).
The trivia items below may give away important plot points.
at around 1h 28 mins) Previous movies in the "Alien" franchise (particularly Alien 3 (1992)) have established that the Alien creatures take on some physical characteristics of the creatures they gestate inside. This film ends with an alien "chestburster" emerging from inside a Predator; the creature has green coloration, an obvious resemblance to the Predator face, and makes the trademark "clicking" noise.
The reason a single Alien kills two Predators in such a short period of time is because the trial inside the pyramid is supposed to be a coming of age ritual for specifically selected Predators, who were young and relatively inexperienced; unlike the Predator "The Wolf" in Aliens vs. Predator: Requiem (2007), this film's sequel, who manages to kill nearly all Aliens he encounters.
Ian Whyte plays all three Predators in this movie, and would go on to appear as the Predator in Aliens vs. Predator: Requiem (2007), as well as the Last Engineer in Prometheus (2012). In all movies, his characters are killed or mortally wounded by Aliens. That means that he is killed off five times by an Alien throughout the entire Alien franchise.
at around 52 mins) The character Maxwell Stafford, played by Colin Salmon, dies in this film by getting pined against a wall and cut into cubes by the Predator's net weapon. This is remarkably similar to the way his character "One" dies in Resident Evil (2002). In that film, he is also cut into cubes, that time by a waffled laser beam passing through his body.