Trivia: Tom Cruise broke his ankle doing the building jump in London. He was always intended to almost miss the landing and have to pull himself up, but his foot hit the side of the building and was forcibly bent at a wrong angle. Filming was held up for seven weeks. When he limps away once he has climbed up to the roof, he's not acting - that's the result of his injury.
Trivia: Spoilers. You can briefly see at one point that Margot's high school mascot is an anthropomorphic catfish. In internet slang, "catfishing" is when someone pretends to be someone else online in order to "lure in" others. This is a very subtle clue to the ending, in which it is revealed that the user "fish_n_chips" was a boy who was "catfishing" Margot online.
Trivia: Contemporary or modern-day altered version of the "BTK" (Bind, Torture, Kill) serial killer - Dennis Rader - who murdered at least ten women from 1974-1991 in the Wichita, Kansas area. Rader was arrested in 2005 and received ten life sentences, but the "Clovehitch Killer" was killed by his son and made to look like an accident or suicide.
Trivia: Following the success of this film, Netflix had to release a statement begging views to not try the "Bird Box Challenge" that was sweeping social media and putting many people in hospital. A news article on the incident can be viewed here https://www.theguardian.com/film/2019/jan/03/netflix-bird-box-challenge-meme-sandra-bullock-blindfold.
Trivia: Although the post script states Dora Block was killed in the raid, she had been taken to hospital a few days earlier and wasn't present. She was murdered by the Ugandan Secret Police in reprisal a few days after the raid.