A24’s brilliant family horror Hereditary has already cemented itself as one of — if not the most — terrifying movies of 2018. Months before its release, its chilling trailer teased out some of the more bizarre behaviors of one character, Charlie (played by Milly Shapiro), among them tongue-clucking.

That habit was brought sharply into focus as a plot device throughout Ari Aster’s hair-raising feature debut. For those wondering about 13-year-old Charlie’s tick, Aster told Inverse’s Eric Francisco it was a script device that became “more of a thing” than he’d originally thought it would be (likely thanks in no small to A24’s brilliant marketing ahead of Hereditary’s official release).

“It was simple, and it was easy to establish and memorable,” he said. “It’s become more of a thing than I ever anticipated, which I’m happy about.”

“Memorable” is certainly one way to describe the performance by Shapiro, whose execution of the role using the Stella Adler method (a style of imaginative acting pioneered by the actress of the same name) tapped into animal characteristics to bring Charlie’s complicated persona to life.

“For Charlie, I chose her outer animal — which is basically the physicality — I chose a turtle because she likes to go inside of herself, and she’s always trying to be hidden,” she said last week in a screening Q&A at Brooklyn’s Alamo Drafthouse. “And then for her inner animal, I chose a snake because snakes are usually seen as something evil, but they’re also misunderstood. So I thought that would help me with the character.”

The clucking certainly helped too.

Hereditary opened in theaters June 8.