- Box Office Bomb: Budget, $16 million. Gross, $645,949
. It was only theatrically released in a handful of countries, including Australia and New Zealand, and made very little money, while it was dumped to video-on-demand everywhere else. Even the $6.99 rental generated little to no interest. - Copiously Credited Creator: In addition to directing, co-writing and producing the film, Sia also composed the soundtrack (in the form of new original songs) and did the editing.
- The Danza: Ebo Odom, played by Leslie Odom Jr..
- Dear Negative Reader: In response to criticisms following the teaser trailer, Sia urged people to withhold their judgments until seeing the film, although her knee-jerk attempts to defend herself did not give her a good look.
- Descended Creator: Sia portrays a caricature of herself, credited as "Popstar Without Borders".
- Direct to Video: It went straight to video-on-demand everywhere except for a handful of countries.
- Dyeing for Your Art: Kate Hudson shaved her signature long blonde hair off into a buzz cut for the role. Due to the three-year editing process, it had all grown back by the time the film was actually released.
- Extremely Lengthy Creation: Sia conceived the film sometime in the mid-2000s as a short story, before later befriending an autistic man, Stevie, at her A.A. meetings, and began developing the story into a film based on him. She wrote at least two screenplays (non-musical and musical) throughout the 2010s before the film was finally filmed in 2017. Due to personal issues, Sia struggled throughout the editing process, pushing the release to 2021.
- Fake Nationality: Ebo is said to be from Ghana, but his actor, Leslie Odom Jr., is from Queens, New York City.
- Flip-Flop of God: There was confusion when Sia claimed that Music was originally played by an actress with non-verbal autism but had to drop out "because it was too much for her", and then was replaced with Maddie Ziegler, although 2015 interviews seemed to suggest that Sia was eyeing Ziegler for the role from the beginning. However, it remains unknown, seeing as Sia was writing a different film in mind for Ziegler at the time.
- Lying Creator: In light of complaints about a scene that depicted Music being physically restrained in a chokehold ("crushing you with my love") during a meltdown — in fear that it would normalize a dangerous practice that has injured, traumatized and even killed autistic children and adults in real life — Sia apologised and said the scene would be edited and/or removed from the film. It currently remains unedited.
- Mid-Development Genre Shift: The film was not originally intended to be a musical; changing it into one quadrupled the budget from $4 million to $16 million.
- Typecasting:
- Kate Hudson plays a non-maternal woman who suddenly finds herself as a caregiver for a teenage family member, and has to learn and grow because of it. This is essentially the same as her role in Raising Helen, except it's as a sister this time.
- Maddie Ziegler likewise played a Satellite Character who encourages growth in an irresponsible older woman in The Book of Henry.
- What Could Have Been:
- Zu was going to be a man meant to be played by Shia LaBeouf, with whom Sia was in a relationship at the time. LaBeouf was later replaced by Jonah Hill, who in turn was replaced by Kate Hudson, with the character being gender-swapped, after Sia saw Hudson singing on Instagram.
- Sia's cameo as the "Popstar Without Borders" was originally offered to other pop stars such as Beyoncé and Katy Perry.
- Working Title: Sister.
- Write What You Know: While the character is based on Stevie, a non-verbal autistic friend of Sia's, Sia discussed on a Twitter Space in 2022 that she was diagnosed with autism after the film's release and thus finally understands why she had such a strong connection/interest to the autistic community.
- Write Who You Know: Music is based on Sia's autistic, non-verbal friend Stevie.
This film, alongside Evangelion:3.333 You Can (Not) Redo. and the premiere version of Evangelion:3.0+1.0 Thrice Upon a Time, are the first non-documentary films to be released exclusively on IMAX theatres.
