- Unpublished sequences of Unbreakable:--Mr. Night Shyamalan has been able to incorporate unseen footage from Unbreakable into Glass for scenes depicting the memories of David Dunn or Joseph.
- Shooting:--The filming of Glass lasted 39 days. It began on October 2, 2017. Part of the scenes were shot in a psychiatric hospital that actually existed in Allentown, Pennsylvania. Staci Hagenbaugh, exterior manager, had a track that could match the expectations of the production.
- 19 years later:--19 years after Unbreakable, Spencer Treat Clark and Charlayne Woodard are back in the roles of David Dunn's son (Bruce Willis) and Elijah's mother (Samuel L Jackson).
- Shyamalan psychologist:--Where Unbreakable followed a man whom his modest image of himself had blinded to his true power; where Split explored the mortal power of a monster created by a traumatized mind, Glass is interested in the very essence of identity by asking a question: are we objectively what we are, or rather the physical result of what does our mind shape and determine? Are you a superhero if you think you are, even if it's just a fantasy.
- Split, McAvoy and Joaquin Phoenix:--Initially, it was Joaquin Phoenix who was to play Kevin's role in Split and filmed for the third time under the direction of Mr. Night Shyamalan, after Signs and The Village. Unfortunately, the discussions with the actor never succeeded and it is ultimately James McAvoy who inherited the character.
- Build each personality:--Every personality played by James McAvoy had to have a distinct voice and presence; the director and the actor therefore worked to define each identity.
- Terrifying images:--To create a terrifying and dark atmosphere, Mr. Night Shyamalan appealed to the director of photography, Mike Gioulakis. The latter is none other than the person responsible for the oppressive atmosphere of It Follows, the little surprise of the horror / horror genre released in 2015. It is also after seeing this film that the director of Sixth Sense decided to to hire the services of the chief operator for Split then Glass.
- Impro or not improve:--While Mr. Night Shyamalan is keen to follow his script to the letter, he nonetheless encourages actors to contribute.
- Anya Taylor-Joy soulmate of McAvoy:--Anya Taylor-Joy has such an intense connection with her character that it scared her to find him.
- A troubling actress:--The talented young actress Anya Taylor-Joy, only 22 years old, held the top bill in Split before returning to her role as Casey in Glass. The actress was revealed in the horror film The Witch, very noticed when it was released in June 2016.
- Principal photography on the film began on October 2, 2017 in Philadelphia, following a week of rehearsals. Shyamalan planned for a 39-day shoot in this period. On October 31, 2017 it was reported that Shyamalan was filming at the Allentown State Hospital for the film and would be filming there for a few weeks. On December 12, Shyamalan revealed that 4 scenes are being planned to be shot in January 2018, stating he'd have to travel for those. On February 16, 2018, a scene was filmed at Bryn Mawr College in the athletic center.
- Sam and Bruce, 5th!:--Glass marks the 5th collaboration between Bruce Willis and Samuel L. Jackson after Fatal Alarm, Pulp Fiction, A Day in Hell and Unbreakable.
- MG Initials:--One of the biggest advantages of working with actors who have all played their characters before is that they bring their own ideas for certain clothes and accessories. For one scene, costume designer Paco Delgado had dressed Elijah Price with a tie with a hairpin, but the artist was not satisfied with the hairpin.
- Visual effects:--One of the hallmarks of Mr. Night Shyamalan's films is the seamless integration of visual effects into a real world. Unlike almost every other great studio movie - and certainly every superhero movie - its effects never draw attention to them. In appearance, it is often impossible to say which elements, if any, are computer generated. This is explained both by a pure creative will and by practical considerations.