The Mouse This Roared tells the story of the fictional European principality of Grand Fenwick. Finding itself on the wrong end of a trade dispute together with the United States, and noting America's generosity in rebuilding the countries it had fought in World War II, Grand Fenwick's rulers hit upon the idea of declaring war on the U.S., losing, and then reaping a Marshall Plan-style handout. The plan, proposed by Grand Fenwick's prime minister (played by Peter Sellers), is approved by the monarch (in addition played by Peter Sellers), who dispatches an invasion force under the command of Grand Fenwick's hapless Field Marshal (in addition played by Peter Sellers). Due to a series of happenstances and misunderstandings, however, Grand Fenwick's plan goes terribly wrong... --Andrew Mueller