Leigh Whannell explained how he conceived the werewolf's point-of-view shots, saying: "I had this idea of the camera moving around the room and suddenly what seemed like gibberish became legible, and you realized there was some invisible wall that the camera had crossed through. I started researching wolves, how they see, the colors of their eyes. I was thinking about how animals hear. When we talk to our dogs, we all anthropomorphize our pets. I have whole conversations with my dog where I'm like, "What are you doing? Oh, you're upset. What are you upset about?" You know that he's just staring at you. They recognize tone and maybe up to 20 words. I was thinking about that. This classic Wolf Man story is a great way to use this because usually in Wolf Man stories, the transformation is very quick. I was like, what if you slowed this down and treated it more like a degenerative illness? I was thinking more of a film like "Still Alice."
Leigh Whannell and his wife had a very close friend in Los Angeles suffering from amyotrophic lateral sclerosis [ALS, also known as motor neurone disease or MND], that takes over your body. He explained "It's heartbreaking when your body turns against you and begins shutting down; it's a real-life horror movie for both the person suffering and the people left behind." Following his friend's death, Whannell channelled his grief into this film as a way of processing what had happened. "It was important to us to reflect on some idea of this waking nightmare and to try and capture the fear Blake experiences as he feels himself slipping away," says Whannell. "That's the scariest part; people that have these types of diseases fight to try and maintain some semblance of themselves."
Julia Garner, said that the first time she saw Christopher Abbott in the "incredible" prosthetics "I could not stop looking at him. It was very weird and bizarre. And I was just like, 'Oh my God, this is terrifying.' And then I got used to it after like, three days." She added, "I think, actually, it's more scary when it is a slower transition, because I still recognized little elements of Chris. His skin and his hair were changing, but he still had his eyes. And I think if you want to make anything scarier, just go with something familiar."
Christopher Abbott watched hours of animal videos on YouTube to grasp the wolf's body language. "There's different levels as the process is happening. There's maybe 80 percent human, 20 percent animal, and then that shifts. So to track how a human would react to something as opposed to an animal; a human reacts one way, if it feels ill or if it's scared, as opposed to how does an animal act, how, if it feels ill, all its little levels," he explained.
The moving truck in the film is a (fictional) company called Pierce, which has been in business since 1941. The name references Jack Pierce, who was Universal's classic monster make-up artist in their 30s and 40s heyday. 1941 references the year Universal's original The Wolf Man film was released.