- Awesome, Dear Boy: Toni Collette had told her agent that she didn't want to do any more heavy, dark films and only wanted to do comedies, but upon receiving Hereditary's script, she loved it so much that she was mildly infuriated that she couldn't turn it down.
- Breakthrough Hit: For Ari Aster.
- Dawson Casting: Milly Shapiro, 16 at the time of the film's production, portrays 13-year-old Charlie Graham.
- Deleted Scene: One has officially surfaced, consisting of a small exchange between Peter and Charlie before they head into the party.
- Dyeing for Your Art: Toni Collette stated that she went to the gym a lot during shooting because she needed to be moving around during such an arduous filming process.
- Enforced Method Acting: Alex Wolff offered to break his nose for real in the scene where Peter slams his head into a desk, but Aster respectfully declined and told him they would be using a soft, cushioned foam desk. When he arrived on set to shoot the scene, Wolff realized that the desk he'd be using was in between both of their ideas — only the top half was foam, and the bottom was very much hard. For added pressure, there were only two desks made, so he had only two takes to get it right. The extent of Wolff's injuries reportedly included his nose getting damaged, blood gushing down his knee from hitting the desk, losing his voice, being unable to move his arm, and his ankle swelling, so all things considered, the extreme pain you see Peter in afterwards is coming from a very real place.
- Fan Nickname: The movie itself has been referred to by many people as "Her head-itary".
- Method Acting: Aster requested that Alex Wolff and Milly Shapiro go out to eat in character a few times, and they would sit for up to three hours in silence while Milly wouldn't speak and Alex would try to get her to talk.
- Those Two Actors: This wasn't the first time that Gabriel Byrne and Alex Wolff had played father and son in a project. 10 years prior, Wolf played Byrne's child in In Treatment.
- What Could Have Been:
- The rough cut of the film ran over three hours. According to director Ari Aster, most of the deleted footage was dialogue exchanges between the family.
- According to early test screenings, the ending was slightly more on the graphic side. After the crowning is complete with Peter, he then rips his eyes out to finish his transformation into Charlie/Paimon. This would also act as a payoff to all of the pictures we see of Peter and eyes sketched out.
- Word of God: According to director Ari Aster, Charlie has in a sense been Dead All Along, the "real" Charlie having essentially been displaced since birth and her body used as a vessel for Paimon the entire time. The film hints at this, including how out-of-character and bewildered she seems to be when Annie channels her during the seance.
Trivia / Hereditary