Tyrell (Martin Wallström) and Joanna (Stephanie Corneliussen) don't speak the same language: He speaks Swedish and she speaks Danish. The languages are both so similar that native speakers normally can carry on conversations the way Tyrell and Joanna do (The closed captions incorrectly identify both languages as Swedish).
1981 video game Donkey Kong is heard at fsociety base.
Romero (Ron Cephas Jones) breaks the fourth wall when he says "right now some writer's working hard on a TV show that'll mess up this generation's idea of hacker culture" referring to the show.
During his hallucinations Elliot (Rami Malek) sees Error 404 Not Found error message in the place where a house moments ago was standing. 404 error message is an H*TP standard response code indicating that the client was able to communicate with a given server, but the server could not find what was requested, referring to the house that Elliot was looking for.