Writing a tentpole summer movie can mean huge rewards, but it's also rife with extra pressures. An exercise in politics as much as creativity, these colossal productions often require a screenwriter to collaborate not only with directors and producers, but also with the toy industry, comic-book companies, merchandising entities, rabid fans, marketing execs, storyboard artists, the laws of physics, previous movies and source material and, often, a host of other unseen writers.