- Approval of God: Debra Tate was initially very apprehensive about the project as she feared the murder of her sister Sharon would be salaciously exploited (she's been defending her sister's memory against exploitation for decades), but after talking with Quentin Tarantino and reading the script, she gave it her blessing.
- Artist Existence Failure: Burt Reynolds was initially cast as George Spahn, but succumbed to a heart attack before shooting began. Bruce Dern replaced him in the role.
- Channel Hop: The film, like Tarantino's previous three movies, was initially to be produced by The Weinstein Company. Following the company's big troubles due to the sexual abuse allegations on Harvey Weinstein, Tarantino looked for a new production house. The project ended up at Sony Pictures.
- Dawson Casting: Producer Marvin Schwartz was 41 in 1969. He's played by Al Pacino, who was 78 during the filming.
- Dueling Movies: This movie is actually the second in 2019 to take inspiration from the Manson Family murders. A few months previously came The Haunting of Sharon Tate, a horror movie starring Hilary Duff that was panned upon release and quickly forgotten.
- Dyeing for Your Art: Leonardo DiCaprio undertook a strict workout routine in order to convincingly play an action star, giving up pastas and desserts and doing hundreds of push ups per day.
- Meaningful Release Date: The film comes out fifty years after the murders that were committed by the "family" of Charles Manson and took the life of Sharon Tate. It was actually set to come out on the anniversary day (August 9) but was pushed back one week by Sony out of respect after Debra Tate (Sharon's sister) called the initial release date "tacky and exploitative".
- Posthumous Credit: Luke Perry died in March 2019 from complications sustained after a massive stroke before the release of the film, which is consequently the last work he had contributed to.
- Production Posse: As usual, Tarantino brought some veterans of his filmography in — Brad Pitt from Inglourious Basterds, Leonardo DiCaprio from Django Unchained, Bruce Dern from Django Unchained and The Hateful 8, Kurt Russell from Death Proof and The Hateful 8, and Zoe Bell from Death Proof and Django Unchained.
- Release Date Change: The film was initially set for release on August 9, 2019, the 50th anniversary of the murder of Sharon Tate, before being moved by Sony out of respect for the victims and Sharon Tate's family.
- Role Reprisal: Damian Herriman reprises his role as Charles Manson from Mindhunter.
- Starring a Star as a Star:
- Those Two Actors: Margot Robbie and Leonardo DiCaprio are reunited six years after The Wolf of Wall Street.
- What Could Have Been:
- Tom Cruise was considered to star as Cliff Booth but had to back out due to scheduling conflicts with Top Gun Maverick.
- Samuel L. Jackson was in talks for a role.
- Regular Tarantino contributors Tim Roth and Michael Madsen, plus James Remar who appeared in one of Tarantino's prior films, all filmed scenes for the movie, but they were cut for time.
- Working Title: #9, as this is Quentin Tarantino's ninth film.
Trivia / Once Upon a Time in Hollywood