The Mouse That Roared is a 1959 comedy film starring Peter Sellers in three roles, based on the novel by Leonard Wibberly about the tiny Duchy of Grand Fenwick and its plan to save its economy by declaring war on the United States of America, losing, and benefiting from foreign aid and reparations. By sheer accident (and kidnapping a scientist with a valuable new bomb), the country actually wins the war, causing new complications.
A sequel film followed, The Mouse on the Moon (1963), also based on a Wibberly novel, with most of the same characters but an almost entirely different cast.
- In the 1976 book How to Be a Grouch, posters at a Grouch movie theater include one for The Grouch That Roared. In this case, rather than a metaphor for the underdog succeeding, the title appears to be meant literally.
- Timothy Bateson played soldier Roger in The Mouse That Roared
- John Bluthal played Von Neidel in The Mouse on the Moon
- Stuart Freeborn supervised Peter Sellers' makeup in The Mouse That Roared
- Hugh Lloyd played a plumber in The Mouse on the Moon
- Peter Sellers played Tully Bascombe, Grand Duchess Gloriana XII, and Prime Minister Count Rupert Mountjoy in The Mouse That Roared
- John Wood played a countryman in The Mouse on the Moon