While often compared to other great leading men due to his skill as an actor, Longlegs director, Oz Perkins, recalled a story from production during an interview where he learned Nic Cage has a particular skill that he says no other actor possesses: the ability to recognize how high or low he is able to speak without messing up the audio. The story goes, according to Perkins: "The sound guy came over to me one day...(he) comes up to me a couple of days into Nic being on set and he's like 'Oz, I've never seen anything like it. When Nic is mic'd, I'm watching the dials, when Nic goes big, he goes *right* to the line. Anything more, a decibel or two over that, and it would be hard to use. Then he goes down, he goes soft and his whispering and he's barely talking, he goes right to the line. Anything past that line, you wouldn't be able to use it. He knows where the lines are. It's the craziest thing I've ever seen in my life'."
Despite the praise and acclaim of his portrayal as Longlegs, Nicolas Cage has stated this will be his first, and only, portrayal of a serial killer for film. In an interview with IndieWire, Cage said "I know that the phone's going to be ringing off the hook to play serial killers after 'Longlegs.' And that's not really what I like to do. I don't like violence. I don't want to play people who are hurting people."
Many of Longlegs' encrypted messages contain misspellings and poor grammar after being decoded. This is an homage to the Zodiac Killer, who was also known for his coded messages containing typos, which often made it more difficult to decode his message.
Longlegs quotes the poem "Satan Says" by Sharon Olds in his messages. This poem is about a girl locked in a cedar box being told by Satan that he can get her out if she blasphemes against her family. She does so, but Satan then seals her in the box and leaves her there.
Nicolas Cage and Oz Perkins made the movie as a tribute to their mothers.