Alien: Out of the Shadows
- The publisher's summary on the back on the novel incorrectly states the Nostromo was a salvage vessel, when in fact it was a cargo tug.
- At the start of Aliens, the harpoon gun that Ripley used to kill the Alien can be seen still wedged under the hatch aboard the Narcissus. Thus, the door cannot possibly have been opened at any point between the films, as doing so would have dislodged the gun. This renders the events of the book impossible.
- A major plot point in the novel is the fact that there is only a single hypersleep tube aboard the Narcissus, thereby severely complicating any escape attempt involving more than a single individual. However, the Narcissus is actually equipped with two cryotubes, as can be seen in some shots in Alien.
- In the audio drama adaptation, Ripley repeatedly displays an improbable degree of knowledge regarding Xenomorph biology. For example, she knows that the adult creatures have acidic blood, despite never seeing any evidence of this beyond the Facehugger stage in Alien. She also is somehow aware of their use of an inner jaw as a weapon.
Alien: Sea of Sorrows
- The novel mentions that the USM Auriga crashed into France at the end of Alien Resurrection, yet the film clearly shows that it hits Africa. This confusion may have stemmed from the final scene in the Special Edition of the movie, which shows a post-apocalyptic Paris. However, the film never implies the Auriga is responsible for the city's destruction.
- In the previous novel, Hoop states the detonation of the fuel cell in the mine on LV-178 will turn everything within one mile into "a cloud of radioactive dust". However, when the mine is rediscovered it is still largely intact; while parts are said to have collapsed, the damage is nothing like as extensive as Hoop suggested, and the difference is too great to be put down to overestimation.
- The mercenary team is said to consist of 35 members, yet over the course of the book, 38 individuals are named. Furthermore, Llewellyn simply disappears without explanation towards the end of the book.
- One of the characters is referred to as a woman before being incorrectly referred to as a man.
- When Rollins informs Decker of Ellen Ripley's actions aboard the Nostromo, she tells him that Ripley destroyed the vessel 318 years ago. However, the book takes place in 2497, and 2497 minus 318 is 2179 — the year Aliens is set. Ripley actually destroyed the Nostromo 57 years prior to this, in 2122.
Alien: River of Pain
- The back cover of the book includes an image of a sign stating Hadley's Hope was founded in 2179. This is the year the events of Aliens (and therefore the book) occur. In Aliens, Van Leuwen states there has been a colony on Acheron for around twenty years prior to this date, and this information is in fact borne out in the novel itself; only the back cover is incorrect.
- Newt's birthday is given as March 15, 2173, which would make her six years old by the time of Aliens. However, according to Alien3, Newt is around 12 years old at that time. Additionally, in Aliens, Ripley picks up Newt's "Second Grade Citizenship Award" when she catches her in the vents; second grade students are traditionally 7 to 8 years old.
- The novelization of Aliens by Alan Dean Foster specifically states that there were no soldiers at Hadley's Hope prior to Lieutenant Gorman's team arriving. Similarly, while the film never outright confirms that there was no preceding garrison at the colony, the Marines in the movie do not mention it, nor do they show any concern for their missing fellow Marines (which soldiers would invariably do). Both of these facts contradict River of Pain, which states a whole platoon is stationed at the colony before the Xenomorph incident.
- When Jernigan is inspecting the Narcissus, he notes that there are scrapes and scratches around the door and a blast-scar close to the engines (from when Ripley killed the Alien in Alien). However, in Aliens, Van Leuwen states that no physical evidence of the Alien was found when another team investigated the shuttle.
- When Jernigan and his salvage team board the Narcissus, they find the harpoon gun Ripley used to shoot the Alien lying on a computer console inside. In Aliens, the gun is visible still wedged under the door when they cut in. Although its position in the book is inconsistent with the film, this is clearly supposed to tie in to Alien: Out of the Shadows.
- Daihotai Tractors, often referred to as "crawlers" in the book, are described as having six wheels. These vehicles actually have eight wheels.
- Colonists Curtis and Otto Finch are stated to have been on Acheron for 47 months by 2179, yet earlier the novel places Otto Finch at the opening ceremony for the colony's recreational center, held shortly after the birth of Rebecca Jorden in 2173. This is some six years earlier, which would mean Otto must have been there considerably longer than 47 months (47 months is actually a month shy of four years).
- During the mission to rescue the men stranded in the malfunctioning Atmosphere Processor, Captain Brackett orders Corporal Pettigrew to stay behind inside the tractor as backup, yet several pages later the book lists Pettigrew as being among the Marines inside the processor.
- Some of the dialogue during Ripley's tribunal on Gateway Station does not match that which is actually spoken in Aliens.
- Throughout the scene where Lydecker and Simpson discuss Russ Jorden's request for clarification of his claim rights, almost all of their dialogue differs from what is actually said in the extended Special Edition of Aliens.
- When the Jordens find the derelict, Anne asks if they should call in the find, before Russ responds, "Let's wait until we know what to call it in as." This conversation takes place outside their tractor in the book, but in the Special Edition of Aliens, they have it before leaving the vehicle.
- There are several Eggs in the Pilot chamber aboard the derelict, covered with a blue mist just like those found by the Nostromo crew in the hold. However, these Eggs were not there in Alien (nor in Alien: Isolation) but in the cavern below.
- Hadley's Hope administrator Al Simpson has a moustache in the book, yet he does not in the Special Edition of Aliens.
- When sneaking through the vents to the med lab to spy on Russ, Newt, Timmy and Aaron have to slide down an inclined shaft (similar to the one Newt falls down before she is captured in Aliens) before the end up at a grate overlooking the med lab. However, Aliens shows that the med lab is on the top floor of the main administration block — the children would have to go up to reach it, yet they actually do the opposite.
- While discussing the Facehugger with a revived Russ and his wife, Dr. Komiskey calls the creature "a possible endoparasitoid species". The definition of an endoparasite is "a parasite that lives inside another animal and ultimately kills it", yet at this point no one has died and there is no indication Komiskey knows there is anything inside Russ, making her classification of it nonsensical from a character point of view.
- Stamovich is labelled a Corporal early in the story, yet later his rank is given as Private.
- Simpson quite clearly states that he has sent a message to Gateway informing them of the escalating Xenomorph outbreak and requesting urgent assistance, yet in Aliens the loss of contact with the colony is considered mysterious and no one (Ripley notwithstanding) has any idea what has happened there until the Marines discover the Xenomorphs for themselves. The situation would not be considered so mysterious if the inhabitants had recently sent a distress call mentioning a hostile alien lifeform.
- The M41A Pulse Rifle is erroneously referred to as a "plasma rifle" several times in the book. The M41A is actually a conventional projectile rifle that fires bullets, not plasma.
- The book says the service tunnel that links the colony complex with the Atmosphere Processor originates from the "main floor" (presumably the ground floor) of the colony. However, in Aliens Hudson quite clearly states the tunnel links "into the sub-level" of the colony.
- When Captain Brackett and the other Marines enter the Atmosphere Processor in search of the Xenomorph Hive, they call the elevators and they come up from below. However, Aliens shows us that the elevators return to the landing pad, at the top of the structure, when not in use. As such, the elevators should descend from above when the Marines call them.
- The operations center is said to be above the colony's med lab, when in fact it is next door in the film. The book also states the operations room only has "one way in and out", when in Aliens the room clearly has two entrances — the main doorway (which Hicks and Vasquez weld shut when operations is attacked) and a second door to the rear that leads to the med lab (through which Ripley and the others make their escape during the assault).
- There is no mention at all of the "last stand" discovered by the Marines in Aliens. According to Private Drake, "They sealed off this wing at both ends. Welded the doors and blocked off the stairs with heavy equipment." None of this is seen or even mentioned as having taken place in the book, despite the fact the final surviving colonists hole up in operations.
- As Brackett and the few surviving Marines prepare to evacuate, Private Yousseff points out that the scientists' escape ship has room for "five or six passengers", yet there is no way she could know this — nobody outside of the Weyland-Yutani science team were even aware of the ship's existence until a few minutes earlier, when Dr. Hidalgo told Brackett about it just before she died, and Yousseff was on the other side of the colony at the time. Moreover, Hidalgo never actually revealed how many people the vessel could hold — Sergeant Draper did ask this question, but the doctor succumbed to her wounds before she could reply.