Several websites say a variation of the line appeared that same year in the book (not the film version) of THE GRAPES OF WRATH: chapter 18 of Steinbeck's novel reportedly has the line I know this man -- a man got to do what he got to do. Reportedly by 1962 the line was already a cliche and was used mockingly in an episode of The Jetsons. George Jetson says: Ha, 'a man's gotta do what a man's gotta do'. I should've won three space Oscar awards.