Trivia: This is the third film in the X-Men franchise to make reference to the villain Mr. Sinister, following X-Men: Apocalypse and Deadpool 2, by way of the Essex Corporation (Nathaniel Essex being Mr. Sinister's real name). The logo for the Essex Corporation is a diamond, similar to the ones Mr. Sinister has on his forehead and chest in the comics. Unfortunately, since this is the final film in the Fox X-Men franchise, Mr. Sinister himself never made a physical appearance in any of the films.
Trivia: The film has had a notorious post production - especially when it comes to the release date. The film was originally scheduled to be released in April 13, 2018. However, it was pushed back to February 19, 2019 to make time for reshoots. It was then pushed back to August 2, 2019 due to the Disney/Fox merger. It was subsequently pushed back again April 3, 2020 so it wouldn't come out so close to "Dark Phoenix." And then, because of the COVID-19 pandemic, it was pushed back again to August 28, 2020 - nearly two-and-a-half years after it was originally supposed to come out.