The car driven by Richard Kiley throughout the film is a Pegaso, an expensive Spanish-made racing/sports car.
Director Don Siegel was so unhappy with the way this film turned out that he later said, "If I knew the Spanish word for 'ech!', I'd use it".
The film was made on location in Madrid using the same cameras and auxiliary camera equipment as Funny Face; Paramount had shipped the equipment from Los Angeles to Paris, then held it over in Europe for this production after the Fred Astaire/Audrey Hepburn project had wrapped.