All the German-speaking characters have a decent pronunciation except Krieger, who speaks German with a super thick American accent.
The national hot dog day, which Archer and Poovey refer to, actually exists.
Upon arriving at the mansion, Archer references The Ghost and Mrs. Muir (1947), which is a story of a young widow who falls in love with a ghost.
The meeting in the greenhouse between Archer and the Tunts is an homage to the opening scene of "The Big Sleep" where Phillip Marlowe meets General Sternwood. That Archer asks for a drink and does not get one alludes to an aspect of that scene.