Due to laws set in place after World War II which made it illegal for any media, outside of education, referencing the Nazi Party to be sold in Germany, the game had to be censored and changed greatly in order to receive classification. This included changing the Nazis to the Regime and the remodeling of assets that included Nazi paraphernalia to reflect the Regime's symbols. Because of this, it became the first Wolfenstein game to ever be released in Germany.
Contributed by totallytman
In chapter 7, two vault doors with the number "101" written on them can be found Spoiler:in the Kreisau HQ hangar. This is a reference to Fallout 3, in which game's main character grows up inside "Vault 101".
Contributed by DoctorWhat?
In the resistance hideout, there is a bed next to a wall with Wolfenstein 3D artwork on it. If the player interacts with the bed, they will enter a "Nightmare", which is a remake of the first level of Wolfenstein 3D.
Contributed by eronecorp