There are many references to other Bethesda games in The Old Blood. There's a Quake bazooka on the car key at the start of the game, there's the iconic horned helmet from Skyrim which can be used for armor, and there's a Nuka Cola label on a vending machine from the Fallout franchise.
Enemy Soldier:
Papers, please.
Rudi Jager:
Hold it.
Rudi Jager:
Frankfurt? Are you a Frankfurter?
William 'B.J.' Blazkowicz:
Yes. Eh, a... ''Hot dog''.
Rudi Jager:
Funny guy! Like those stupid Americans say! ''Hot dog''! They'll see when we take over. Carry on.
Rudi Jager:
Greta. Heel.
When Rudi interrogates B.J. he stabs him in the leg with a broken drain pipe (a weapon used in the game), but B.J. feels no ill effects from it (e.g., limping, blood loss)
German version was modified to remove all Nazi references (e.g. all Swastikas were removed, the Third Reich became The Regime).
English, German