Klaatu is a fictional character from the 1951 science fiction film The Day the Earth Stood Still. He is an alien visitor who arrives on Earth in a flying saucer, accompanied by a powerful robot named Gort. Klaatu's mission is to deliver an important message to humanity about the dangers of war and the need for peaceful coexistence. In the film, Klaatu takes on human form to better communicate with people. He seeks to unite the nations of Earth and warns that if humanity does not change its ways, it may face dire consequences. The character has become an iconic symbol of extraterrestrial diplomacy and cautionary tales about technology and conflict.