The Man Called X original aired from 1947 to 1952 on CBS radio and later NBC. Herbert Marshall had the lead role of agent Ken Thurston("Mr. X"), an American intelligence agent who took on dangerous cases in a variety of exotic locations. Leon Belasco played Mr. X's comedic sidekick, Pegon Zellschmidt, who always turned up in remote parts of the world because he had a "cousin" there. Zellschmidt annoyed and helped Mr. X.
The man called X was adapted for TV in 1956. Airing only 39 episodes, before it was canceled in 1957.