Approximately ninety minutes of gameplay before the opening credits roll.
This is the ninth installment in the Wolfenstein series.
In the mission "A New World" when you are clearing out the first of 3 outposts of Nazis, there is a shed with watermelons on a table beside it. If you look at one of the walls there are three pieces of paper pinned to it with crude drawings, two of Frau Engel and the other of her companion Hans Winkle (AKA Bubi). If you look, there is a knife stuck in one and there are holes in all three because soldiers have been using them for target practice with knives.
Some Nazi soldiers speak English. This is based on the famous conspiracy theory during the Battle of The Bulge where Allied soldiers captured Nazi Soldiers who were fluent in English (according to the theory).
In the Kreisau Circle HQ, you can see a wooden board with the letters, "IDKFA". This is an old and famous cheat code for Wolfenstein's sister game Doom which will give you all of the weapons in the game as well as all keys, full ammo, and armor.