- Troubled Production: The film has had a troubled post-production.
- Following test screenings (which were rumored to not have gone over very well, although this point is disputed), Fox decided to push the movie back ten whole months. One report alleges that the movie wasn't seen as scary enough and that the film needed to be significantly reworked as a result, which isn't exactly reassuring considering that the movie was promoted as being a horror movie over being a superhero movie. (Another report explained that the reshoots were meant to counter percieved Executive Meddling and make the movie closer to Boone's original vision, which had more scares; the same account states that the film tested well.)
- Following that delay, Fox hit the film with a second delay of another six months, with rumors suggesting that as much as half of the film will be reshot. The film will now release nearly 18 months after its original release date, and two years after filming (and its teaser trailer). However, with regard to the massive delays to the movie, several factors are still in play; namely, that actors aren't necessarily available for the reshoots due to other projects, such as Anya Taylor-Joy on Glass and Maisie Williams on Season 8 of Game of Thrones. With Disney's acquisition of Fox, it got delayed once more to 2020, with even the Grand Finale of the series, Dark Phoenix, coming out before.
- What Could Have Been: In a 2018 convention panel, artist Bret Blevins noted that he and writer Louise Simonson planned a subplot in which it would be revealed that the source of Boom-Boom's brash behavior was insecurity over the fact that she was illiterate, after which her teammates would teach her how to read. This never happened due to the switch-over to X-Force.
Trivia / New Mutants