- Dawson Casting:
- Alex Wolff (Trent), Thomasin McKenzie (Maddox), and Eliza Scanlen (Kara) were all in their late teens or early 20s when they portrayed the film's teenage characters. Wolf and Scanlen both happen to be older than McKenzie, despite McKenzie's character being older.
- Inverted with Emun Elliot, who was in his mid-30s when he played the 50-year-old Trent.
- Disowned Adaptation: Sandcastle artist Frederik Peeters likened the film to an 80's B-Movie (which, he adds in a Take That!, would be equivalent to a Netflix Original in The New '20s). He also didn't care much for the film adding a purpose to the beach, which he intended in the graphic novel to be just an unexplained plot device to enable a philosophical exploration of the ravages of time, but understood that Shyamalan made the changes he did for commercial purposes and because, in Peeters' mind, a faithful adaptation of the graphic novel would last just 45 minutes.
- Fake American: While the characters portrayed by the Mexican Gael García Bernal (Guy), Luxembourgish Vicky Krieps (Prisca), and English Rufus Sewell (Charles) reflect their respective performers' non-American nationalities, most of the American characters are also played by non-Americans, specifically New Zealander Thomasin McKenzie (Maddox), Australians Abbey Lee (Chrystal) and Eliza Scanlen (Kara), English performers Nikki Amuka-Bird (Patricia) and Aaron Pierre (Mid-Size Sedan), South African Embeth Davidtz (adult Maddox),note and Scottish Emun Elliot (adult Trent).
- Release Date Change: The film was initially set to release on February 26, 2021 but was delayed to July 23, 2021 due to COVID-19 Pandemic-related release shuffles.
- Spoiled by the Cast List: Embeth Davidtz and Emun Elliot were revealed to be portraying adult versions of Maddox and Trent, giving away that the characters would survive long enough to hit maturity. Likewise, the absence of an adult Kara in the cast list gave away that she would not survive.
- What Could Have Been: Shyamalan had tremendous trouble deciding if he would stick to the graphic novels bleak, fatalistic ending or go with his usual style of adding a big shocking Twist Ending. He only made a final decision about a month before the film needed to be in the can. According to a post on Reddit, test screenings didn't even have the ending.
Trivia / Old