Answer
"The Mouse That Roared," a satirical comedy released in 1959, stars Peter Sellers and Jean Seberg. Set in the fictional Duchy of Grand Fenwick, the film revolves around the country's declaration of war against the United States. Sellers plays the dual role of the bumbling Prime Minister and the country's secret weapon, while Seberg portrays an American journalist who becomes captivated by the political intrigue and Sellers' charm.