At first Adam Sandler declined his part because he was terrified of it, although he thought the character was incredible after he read the script. A month later, he reread the script and decided that he wanted to do it.
The video game that Adam Sandler and Don Cheadle play is Shadow of the Colossus (2005). It's a game about a man who slays colossi in an attempt to bring a woman back to life. Early scripts had Sandler play a simple, 1980s-style game, until editor Jeremy Roush recalled that his own father watched the movie Aliens (1986) obsessively as a "thinly veiled kind of Vietnam veteran kind of story". Seeing the imagery of the colossi falling, he realized "someone who was dealing with 9/11 would be engrossed by a giant that keeps collapsing over and over again," so he demonstrated it to the director and actors. With the approval of the game's director Fumito Ueda, it was included in the movie.
The title is inspired by Pete Townshend's song "Love Reign O'er Me" from The Who's 1973 album 'Quadrophenia,' which was also the inspiration for the scooter in this film. The song itself appears twice on the film's soundtrack, the second time during the end credits.
Alan Johnson reads a Captain America comic book and notes that he has a black sidekick, Falcon. Don Cheadle plays superhero sidekick War Machine in the Marvel Cinematic Universe and appeared along with Captain America and Falcon in Avengers: Age of Ultron (2015) and Captain America: Civil War (2016).
The trivia item below may give away important plot points.
Charlie's appearance is reminiscent to that of Pink Floyd's first singer Syd Barrett; who also lost his mind which lead to his departure from the group and lead his life in serious alienation from people.