The Fat Man character, Brad Runyan, was played by Jack Scott Smart

The Fat Man, was a popular detective drama radio show based on characters
by Dashiell Hammett. The series starred J. Scott Smart an accomplished actor
of stage, screen, and radio as well as a musician and music historian.The show premiered on the ABC Radio Network on Monday, January 21, 1946 and ran
until 1951. It was produced by E.J. ("Mannie") Rosenberg, directed by Clark
Andrews, and Charles Powers. Rosenberg was also the creator of Big Town.