The three main stars previously worked with Remedy. Courtney Hope (Jesse) was in Quantum Break (2016), Matthew Porretta was the star of Alan Wake (2010) and James McCaffrey provided the voice of Max Payne in Max Payne (2001) and Max Payne 2: The Fall of Max Payne (2003).
The cigarette machines in The Oldest House sell brands including Dudebro, Jack's Choice and Holy Smokes - but there is also a brand called Payne, a reference to Remedy's previous Max Payne games, which has a logo of a "smoking gun" (literally a handgun with a lit cigarette in the barrel). There is also a carton of Black Pyramid cigarettes in the lobby.
The magazine racks in The Oldest House all contain copies of a magazine titled Game, with the cover story of a "game about secret agents" and an image of a woman with similar hair & body as Jesse Faden, but with a blurred flace.
The janitor Ahti says several Finnish idioms that have been translated to English literally rather than contextually, so they sound like gibberish to most people, but Finns who get these references might get a kick out of them. For example "I am not a son of yesterdays grouse", translated from the Finnish idiom "en ole eilisen teeren poika", is roughly equal to the English idiom "I was not born yesterday", aka "I am not an idiot".
Matthew Porretta said in an interview he based his performance for Dr. Darling after Richard Feynman.