Reportedly, the character of Auntie Mame was based on Patrick Dennis's real-life aunt, Marian Tanner. A good-natured eccentric, who lived to be nearly one hundred years old, Ms. Tanner's advice to those seeking a more interesting, adventurous life was to never be afraid to try a new experience and to keep an open mind about everything and everybody.
Mame's line in French at Macy's is "Après moi, le déluge" ("After me, the flood"). This quote is attributed to King Louis XV of France and represents a philosophy of living for now when disaster looms in the future. In the movie, it relates to purchasing Christmas gifts on credit so that one doesn't have to worry about paying for them right away, something that a rich socialite would be very comfortable with.
The technique Rosalind Russell uses to interrupt and insult Mr. Babcock - "Nuts?" - was previously used against her character "Sylvia Fowler" in The Women (1939) after Sylvia's line "I wouldn't dream of hurting Mary".
The line, "Life is a banquet and most poor suckers are starving to death," does not appear in the book. It is derived from the stage play, where it was originally, "Life is a banquet and most poor sons-of-bitches are starving to death." Though "damn" and "hell" are both heard in the film, "sons-of-bitches" was apparently thought too rough.
Even though the original Broadway play, also entitled "Auntie Mame" was written by Jerome Lawrence and Robert E. Lee, and which was also based on the novel by Patrick Dennis, Lawrence and Lee did not receive any on screen writing credit for this film, only Dennis did.