If you're a Hollywood producer, you have a magical tool. It's called "harassing people." Occasionally, this tool destroys other people's movies. But sometimes…it doesn't.
When Bud Schulberg was writing On the Waterfront, that's what the movie's producer Sam Spiegel did. (Spiegel was head of Horizon Pictures—but the movie was distributed by the better-known Columbia Pictures). He harassed Budd Schulberg, forcing him to make changes. He harassed and harassed and harassed.
And you know what? It worked out. Schulberg made changes to his script, and Terry Malloy became the character we know today.
But, in the process, Spiegel got on Schulberg's nerves in a big way. Schulberg said that he played mind games with him, trying to get him to compete with Kazan, the director.
Also, Spiegel had to make some tough choices. The filmmakers originally told Frank Sinatra he could play Terry Malloy.
When Brando finally decided to act in the movie—overcoming his objection to working with Elia Kazan, who was considered a political pariah by some in Hollywood—Spiegel went back on his promise to Sinatra. He ditched him, and hired Brando for the role. Sinatra was way miffed, but hey—most people would say that Kazan and Spiegel got the right man for the role. What's the matter with a little betrayal?
When the movie was privately shown at an early screening, Brando stormed out. He thought that he'd turned in a horrible performance and the movie was botched. Spiegel apparently made apologetic comments to the composer, Leonard Bernstein, thinking the movie was going to be a dud.
But Elia Kazan yelled at him, "This is a great picture!" He also convinced Spiegel to but his real name and not a pseudonym in the credits—which was nice, since, when the movie won Best Picture, Spiegel could accept the reward under his own name. So, Spiegel didn't know an all-time classic when it was first shown to him—yet, he helped make that classic too. (Source)