The piece of jewelry Marianne Stone wears around her upper left arm was previously worn by her in the Act of Murder (1964) and Lolita (1962).
The birds in the lobby outside Smith's penthouse are hornbills and toucans.
The mystery woman's car in the first part of the film is a 1963 Triumph TR4. The English Girl's car ferried in by air is a 1959 Mercedes-Benz 190 SL. This latter auto, in excellent condition, could be worth well over $100,000 to $200,000 or more at auction in 2019.
As of January 2020, the Mercedes Sports, registration 836MPB, driven by "English Girl", is still in use.