WARNING! The following contains certain spoilers for A Quiet Place!
Aside from a few news articles here and there, we don't know much about the creatures that have rendered the Earth into a silent planet. When the family raids the supermarket in the beginning, we see an edition of The New York Post fluttering in the wind, bearing the headline "IT'S SOUND!"
That's a genius way to exposit plot information and follows one of the most crucial rules of screenwriting: "Show, don't tell." The headline tells us all we really need to know about this universe, and, to a certain extent, the taxonomy and origins of the monsters don't really matter. They're simply a means with which to scare the pants off the audience and drive the story forward.
With that said, Kransinski is breaking his silence on where the movie's main antagonists come from. While making an appearance on the Empire Magazine podcast, he revealed that they do come from outer space, crash-landing on Earth after traveling in meteorites after the destruction of their home planet. His description of the aliens brings to mind the speech about the xenomorph being a perfect organism made by Ian Holm's Ash in the first Alien movie.
“They're an evolutionary perfect machine," Krasinski said. "The idea is, if they grew up on a planet that had no humans and no light, then they don't need eyes, they can only hunt by sound. They also develop a way to protect themselves from everything else – that's why they're bulletproof ... The other idea was it's also the reason why they were able to survive … the explosion of their planet and then survive on these meteorites. Until they open themselves up to be vulnerable, they're completely invulnerable."
One of the TV ads for A Quiet Place, titled "Protect Them," alludes to the monsters' being aliens when a quick voiceover says something about the military fighting "a massive invasion." You might be reminded of the first Alien while watching the film itself during the scene when Emily Blunt's character discovers that one of the beasts has made its way into the soundproofed baby room as water begins to flood the space. It's akin to Ripley (Sigourney Weaver) finding out the xenomorph has stowed away on the escape pod with her and Jonesy after she blows up the Nostromo.
"Where I developed the idea of them and what I wanted them to look like was most alien movies are about takeovers, agendas, they’re a thinking alien creature, and for me this idea of a predator, this idea of a parasite, this idea of something that is introduced into an ecosystem [was interesting]," said Krasinski.
The solution to defeating the creatures, the daughter's hearing aid, was added when Kransinski rewrote Bryan Woods and Scott Beck's screenplay.
“I needed something that the father did to be the thing that defeated the creatures,” he said. “I needed the girl who thought she was the black sheep and the reason for all the horror to be the reason they survived. I needed her biggest weakness to be her superpower […] I love the idea of her not realizing it until the end.”
Even so, the behavior of the beasts and the solution to vanquishing them had to adhere to the strict set of guidelines that Krasinski set up at the very onset of the movie's production.
"I needed the rules of the monster to adhere as tightly to the rules of the family," he said. "The family, we had set up all these incredible rules, and I needed the monster to not just be convenient.”
"I loved the idea of your second and third chance – meaning, if you did make a sound, you go into a whole other level of survival, which is 'Now that I've made a sound, if I run I'm dead, if I stay still I may be dead.' The idea of the Jurassic Park kitchen scene – if you make a sound, you have to stay still and hope that they don't get to you – that was always in my mind."
A direct nod to Steven Spielberg's murderous dino-fest can be glimpsed during the silo scene when the two kids (Millicent Simmonds and Noah Jupe) use the metal door as a deterrent against the monster, which attempts to kill them. It's almost a shot-for-shot re-creation of when the T. rex tries to eat Tim and Lex, who are saved by the glass roof of their tour jeep.