I Spy (1965)

A pair of American operatives work undercover as a tennis pro and his trainer. Kelly Robinson is the man with a racket, Alexander Scott is, among other things, a polyglot. The creation of the Cinemobile for location shooting enabled far-flung episodes in Hong Kong, Europe, Mexico, etc. The writing is of a standard that would be very difficult to match in any circumstances, or as Scott & Robinson might say, the wonderfulness of its marvelousness is only equal to the marvelousness of its wonderfulness.