Dawson Casting: Most of the cast was around fifteen (Aki Maeda as Noriko) or in their late teens (18-year-old Tatsuya Fujiwara as Shuya), but there are still two glaring examples: Taro Yamamoto (Shogo) and Masanobu Ando (Kiriyama) were 26 and 25 respectively when the film was released. The sequel also has a couple of examples, but not many. Makoto Sakamoso, who played Osamu, was 25 when he played the part. Ironically, his character is one of the youngest-looking.
Fridge Brilliance: Both characters are outsiders, and one of them is older. Their actor choice already teases this.
Development Hell: An American remake of Battle Royale has been in this on and off since 2006, usually delayed because of shootings(Columbine, Virginia Tech, Aurora, Sandy Hook). Nobody in a post-Columbine Hollywood could seriously contemplate making a film about high school students killing each other. The shooting at Virginia Tech especially hurt the project. However, the popularity of the Hunger Games movie has given people some hope that it will one day be made.
No Export for You — The two Battle Royale films had never received an official release in the United States, and for years, Toei had insisted on a full theatrical run (with promotion) for at least the first film instead of a mere home video release. No American distributor would accept the deal until Anchor Bay Films bought the license and made plans to release a 3D version of the first film in American theaters in 2011. While those plans didn't pan out, Anchor Bay managed to ultimately subvert the trope by releasing both Battle Royale films on DVD and Blu-ray in the spring of 2012 (chiefly in an effort to capitalize on the publicity surrounding the film version of The Hunger Games).
Real-Life Relative: Noriko Nakagawa and Shiori Kitano are respectively portrayed by sisters Aki and Ai Maeda in the films.