10 Movie Rules That Make No Sense

The Xenomorph is unquestionably one of cinema's most terrifying antagonists, yet it's also fair to say that the creature's physical characteristics have been inconsistent at best across the Alien series' tenure.

By far the most-tinkered with aspect of the Xenomorph is its gestation period within a host's body before inevitably bursting out of their chest.

The original Alien made it clear this took place within a few hours, yet throughout most other entries in the series, this time is basically adjusted to suit a specific film's dramatic needs.

For example, Alien 3 sees Ripley (Sigourney Weaver) survive for several days before being chestbursted, and while some fans have argued that this is due to her being impregnated with a Xenomorph Queen, that feels like a stretch to justify iffy writing.

Things pretty much go all over the place from this point: the atrocious Aliens vs. Predator: Requiem boils the gestation period down to probably less than an hour, and Alien: Covenant follows a similar time-frame.

Again, you can argue that the gestation period differs depending on the biology of the host, but even then, the wide disparity between human hosts is pretty ridiculous.