facehugger phase is totally believable. It’s perfectly adapted for accomplishing what it needs to do. It has a bunch of long spindly legs for wrapping around the front of your head. Then under that there’s a long tail that It wraps tightly around your neck, usually incapacitating you. Point being, once it’s on you you’re not getting it off and it gets to have it’s way with you. It’s pretty sound reasoning. However, everything else about the alien is a little uh… less believable.
On the alien’s life timeline it starts out as an egg, (which always inexplicably hatches precisely when a human walks by it.) From the egg comes your facehugger. The purpose of the facehugger is to find a way inside a host organism, (mostly humans and always through the mouth.) Once it latches on to someone’s face it becomes somewhat mysterious as to what happens and how it’s accomplished. After a while the facehugger falls off of the victim’s face as a sort of dead husk. The victim, now a host to the alien, comes to and goes about life as usual until what is essentially a miniature form of the adult alien bursts out of their stomach and wriggles away into a dark secluded corner. At this point the host is dead.
Now going back to when the hugger first attaches itself to the face, what happened? Clearly the alien entered the host via the esophagus but what’s really weird is that the hugger and what comes out of the host’s stomach are completely different life forms. That’s perfectly acceptable because it happens with butterflies all the time. But when butterflies do it they don’t leave behind a totally intact dead caterpillar. Was the hugger just some kind of vehicle the alien was riding around inside of until it could get out and jump down someone’s throat thereby abandoning it? Or was the hugger a separate entity whose only purpose was to transplant an alien embryo in a nearby host and then die upon success of it‘s mission? But the real point I’m trying to make here is that it already hatched out of an egg, why does it need to further develop inside of a host? Shouldn’t it be more or less fully formed? If it is in fact a transplanted embryo why didn’t it just develop inside.. oh I don’t know, the egg it just hatched out of?! It’s like it has to hatch twice. And what if there was no host nearby or anywhere? Wouldn’t this be an evolutionary dead end? Or if not, it’s just an extremely inconvenient way to propagate your species.
When the juvenile alien exit’s the host, I dare say it’s small enough to cram snugly into a Pringles can. At this point the only thing it has left to do is grow. And holy hell does it grow! It goes from being about a foot tall to around six or seven feet in about half an hour. And somehow it manages to do this without eating anything. One minute it’s no bigger than a chicken and then the next time you see it it’s taller than the crew members. The law of conservation of mass just got suspended.
Another baffling time related discrepancy is how quickly the aliens multiply and establish themselves in a habitat. In the fourth movie, (OK yes it’s not really a trilogy,) a group of aliens get loose on a ship where they are being used as test subjects. No more than an hour later they’ve plastered entire corridors and rooms with their gross membranous snot goo, designated a room for their queen, started an assembly line of egg production in multiple rooms, claimed about a dozen people as hosts, hatched out of said hosts, killed several lab personnel, and created a fully mature human/alien hybrid. I’m aware that there is a difference in movie time versus real life time but in this movie it’s actually pretty similar. If the breakout had occurred at the beginning of the move, the aliens would have had enough time to create an entire civilization complete with night clubs and a sewer system. It almost makes the growth speed of the alien in the first movie look perfectly reasonable.
Something else interesting about the aliens is that they have highly acidic blood. Like so acidic that it can burn through several inches of metal in just a few seconds. I’m willing to let this slide for two reasons. A: I don’t know enough about blood and acid to make a legitimate complaint. B: It’s awesome.
Arguably the coolest feature of the aliens is their mouth within a mouth. Although if you think about it for too long it starts to sound kind of funny. I think I remember watching a Chip and Dale’s Rescue Rangers where Dale is watching an Alien parody on TV. Though instead of having two mouths, this one had like ten. They did have a valid point… if it already has two mouths, why not give it ten or twenty. It’s already outlandish. In the movie the inner mouth extends out of the outer mouth fast enough to puncture a skull and kill prey. So I guess that’s useful. The only thing is that since that mouth has to fit inside another mouth that’s about the size of a regular human mouth it has to be really small. Can you imagine having to eat solid food through a mouth half the size of yours? It would take forever. But since you never really see how the aliens eat I guess it could be argued that the small mouth doesn’t completely block the big mouth and they actually eat with the big mouth. Whatever...
