This is the first time that we see and hear Robin Masters since the passing of Orson Welles, who had originated the role. While his face is never shown, it is clear that he is heavy-set. In this episode, however, we see the back and side of Masters' head. Not only does he not appear to be heavy-set, but the profile and voice seem very familiar.
The title is from the song Mad Dogs and Englishmen written by Noël Coward from the Broadway show The Third Little Show (1931) sung by Beatrice Lillie and then become one of Noel Coward's standards. "Only mad dogs and Englishmen go out in the midday sun."
This is a reference to the British climate, which tends to be gray, cold and rainy for much of the year. No matter how rocky the beach. how cold the water, nor how cool the weather, Britons are teased for the exaggerated notion that they turn out in droves when the sun is shining. The poignant note here is that Higgins thrives in the Hawaiian sun and being forced to return to England is very depressing for him.
This is the second time that we see the four central characters engaged in armed combat. The previous time was when they went to Cambodia to rescue a prisoner of war.