The novel draws upon several sources of mythology, most notably the story of The Fisher King. In other versions the knight Perceval does not ask the king about the grail, so he fails to cure the Wasteland. Pop Fisher is the manager of the Knights and his team is trying to win the pennant, something he has never achieved in his career as both a player and a manager. His name is an obvious reference, along with his need to be "cured" by Roy. Roy Hobbs is the great knight Perceval who is meant to return the Holy Grail (pennant) to Pop Fisher. In Malamud’s version, Hobbs does not win the pennant and the reader is led to believe that Pop Fisher will fade into obscurity.
Roy represents the knight, Perceval, from the story of The Fisher King. Both are uncultured and unintelligent. For example, Pop tells Roy to, "knock the cover off the ball," as Roy goes up to bat. He does just that, and when Pop asks him after why he did that, Roy says it was what he told him to do. When Perceval became a knight, he asked many questions. Finally, his mentor advised him not to ask too many. Consequently, he stops asking questions altogether, and thereby fails to cure The Wasteland.
Alternatively, Roy Hobbs might represent a composite of the flawed hero King Arthur and Lancelot. Each is a heroic character whose lusts lead to his downfall. The name "Roy Hobbs" is derived from the Latin roots of "King" and "horse," implying the chivalric ideal, and the Wonderboy bat has the same invincible properties of both Lancelot's strength and Arthur's sword Excalibur, both of which fail in the final crisis due to the characters' flaws.
The main difference between the film and the novel is the relationship between Hobbs and Iris and the ending. In the film, Hobbs and Iris have known each other since childhood and had a romantic relationship before Hobbs left to pursue baseball. Their brief romance resulted in an out-of-wedlock child that Hobbs never knew existed. At the end of the film, Hobbs hits a home run to win the game and complete his heroic journey and is reunited with Iris and their son. In the novel, however, Hobbs has a tragic flaw; he has a weakness to succumb to his appetites, women, and caring too much about his own glory. These tragic flaws result in the destruction of his Excalibur (Wonderboy), and ends with him failing at his final time at bat. While the film shows Hobbs victorious and fulfilling his dreams of glory, the novel shows a Hobbs who is crushed by his own hubris and must now live as a forgotten man.