The Double Life of Henry Phyfe

The Double Life of Henry Phyfe is a 17-episode American sitcom broadcast on ABC from January 13 to September 1, 1966, and starring Red Buttons.
Plot.
Henry Phyfe (Buttons) was a mild-mannered accountant, until circumstances forced the American Counter Intelligence Service (CIS) to recruit him to impersonate a foreign agent named U-31, who had been killed in an automobile accident. The agent looked just like Phyfe, but the two men's personalities were drastically different. That severe contrast laid the groundwork for many of the episodes.
Phyfe's girlfriend, Judy Kimball, her mother Florence and his boss at the accounting firm, Mr. Hamble, were all unaware of Henry's secret life, with Gerald Hannahan, the regional director of the agency the lone person to know the secret. The characters of the girlfriend and mother-in-law were phased out halfway through the abbreviated run.
Overview.
Buttons noted that, unlike Agent Maxwell Smart in NBC's new hit "Get Smart", his character was shy, used no gadgets in his work, and was an impostor, not an actual agent. Phyfe's CIS boss was played by veteran character actor Fred Clark, who bore a superficial physical resemblance to Smart's "Chief" played by Edward Platt.
The show marked Buttons' return to weekly television after his variety show had ended a three-year run in 1955. During the interim, Buttons found roles in 15 different motion pictures, including an Academy Award-winning performance in the 1957 Marlon Brando film, "Sayonara".
The concept of an "every man" recruited to impersonate someone of importance has been used for many years in literature (for example, "The Prisoner of Zenda"). A few months after the series' cancellation, the animated film, "The Man Called Flintstone", featured the same premise as "Henry Phyfe", while another TV series, "The Man Who Never Was", debuted in the fall of 1966 with the premise reversed as a spy found himself impersonating a businessman who had been killed.