The 1835 Moon Civilization Hoax
In 1835, a New York newspaper convinced the public that the Moon was inhabited by bat-people and blue goats. Readers were captivated by detailed tales of lunar temples and alien beings.
The Sun newspaper published six articles claiming that a famous astronomer had spotted advanced civilizations through a powerful telescope. The reports were so convincing that people clamored for back issues to learn more about the lunar inhabitants. Even after the story was exposed as a complete fabrication, the newspaper’s circulation remained remarkably high. It stands as one of history's most successful and brazen exercises in mass media deception.
Source: Great Moon Hoax