While touching his upper lip, Sykes asks McMillan if he had gotten a haircut. McMillan says, "yes," impatiently and moves on. This is referencing the fact that Rock Hudson had shaved off the mustache he wore throughout the first season.
The portrait of Arthur Kendall was done by Thomas J. Wright, who also did the paintings for Night Gallery (1969).
The stock footage of the Golden Gate Bridge is the same used in the credits of The Streets of San Francisco (1972).
Harry Hasting's castle reappears in the season three episode Death of a Monster... Birth of a Legend (1973), as McMillan Castle in Scotland.
Sharon Acker's character Evie Kendall shares a name with Eve Kendall from North by Northwest (1959), the character played by Eva Marie Saint. Interestingly, it was in another John Schuck series, the sitcom Holmes and Yoyo (1976) in the episode The Thornhill Affair (1976), where the name of Cary Grant's character Roger Thornhill from the classic film is the name used for a character played by Richard Roat (who was in the "McMillan & Wife" episode Husbands, Wives, and Killers (1971)) and a Mrs. Thornhill character is played by Gloria Stroock, who of course played Mac's secretary Maggie on this series for six episodes, being the wife of series creator Leonard Stern till his passing in 2011.