I seem to recall that Winston Groom, author of the original novel ‘Forrest Gump’, was suing the makers of the film. The filmmakers were claiming that the flick didn’t make money, and therefore they had no profits to share with him. Groom of course found this unlikely.
Groom got extra money out of the filmmakers, though no admission of wrongdoing. Sort of “we’re nice guys, so we’ll give you a bunch of money. Now go away.” (I think there may have also been a deal for a sequel.)
Buchwald sued originally for a cut of Eddie Murphy’s COMING TO AMERICA. In contrast to the usual lawsuits about Hollywood “stealing ideas,” Buchwald had a real case – he had been hired by the studio to produce a screenplay that was very much like the final version. The courts ruled that Buchwald deserved a cut. “OK,” said the studio, “we’ll give you a percentage of the net.” Later Buchwald discovered how worthless this was, and sued again. I believe the studio was required to pay up.