Six years ago, a humanoid robot smacked a fly on her neck— and chilled viewers to the bone.

Thus began (or so audiences were led to believe) the unraveling of Evan Rachel Wood’s cheerful cowgirl Dolores Abernathy as she gained sentience and a feverish desire to break herself and other Westworld theme park Hosts free from the whims of brutish wealthy guests.

Much has happened in Westworld since the pilot episode of the HBO sci-fi-western thriller on October 2016. Although flies were consciously included in scenes with “aberrant” Hosts, who were rapidly becoming more human than machine, the flies motif was largely disregarded in Seasons 2 and 3.

“The flies came with an entourage.”

Season 4 brings the flies back, though, in a pivotal way — a tasteful recall back to Season 1, and an unexpected way to bring our modern realities into the futuristic, dystopia of Westworld.

Aaron Paul tells Inverse that most of the flies you see on the show, are, in fact real. “Oh, we worked with a lot of flies! And uh, I don’t very much like flies,” says Paul, who plays Caleb Nichols in Seasons 3 and 4. “There was a fly wrangler, you know, protecting the flies and making sure that no harm came to them. The flies came with an entourage.”

Fly wranglers were used on the show in Season 1 as well. In an interview with the Los Angeles Times, Wood noted that while the flies that get inside of the characters’ orifices are fake, the bugs crawling on her face were not CGI.

This means that Paul may have actually been rather tormented by the parasitic critters that were released by “Charlores” (Tessa Thompson) in Episode 3, swarming around his ears and buzzing on his skin.

“They freeze them while they’re alive,” Wood says. “They take them out and stick them on your face and wait for them to thaw. They then can walk but not fly.”

“They freeze them while they’re alive.”

Back in Season 1, Wood was filmed sitting naked on a stool in a scene with Anthony Hopkins while a fly crawled on her face for about 10 minutes to get the perfect shot.

In Westworld Season 4 Episode 3, it’s finally revealed how the flies take over the bodies of their human hosts as part of a scheme for total robot domination. But what does it mean?

Why Westworld loves flies

New Westworld showrunner and Season 4 writer Alison Schapker— who has credits on Lost, Alias, The Flash, and Altered Carbon— tells Inverse that the flies had to return because of their importance throughout the series, symbolically.

“I literally cannot go to a picnic, or sit in my backyard, or have the same chilled-out experience after the show,” Schapker jokes. “Every time a fly lands, I think of them as little nanobots.”

“Every time a fly lands, I think of them as little nanobots.”

“The fly moment in the pilot was just so iconic,” she adds, “and the idea that, once you saw the fly getting killed, it was like, oh we’re going to wake up this robot. But when, and how?”

Lisa Joy and Jonathan Nolan, co-creators of Westworld, had a vision that in Season 4, Hosts and humans would struggle over the question of symbiosis and coexistence, as the boundaries between the two get more blurred and complicated.

“Humans like to see ourselves as having closed-off boundaries,” Schapker says, “as being invulnerable, which actually leaves us more vulnerable because it’s based on fiction. We really experienced that with the pandemic. In some ways— though not directly —this season was inspired by that in terms of humans figuring out that we’re not, in fact, impermeable.”

Westworld Season 4 is streaming now on HBO and HBO Max.