This Day in History, 1835: The Great Moon Hoax

One hundred and seventy years ago today, the New York Sun newspaper published the first in a series of articles claiming that astronomer Sir John Herschel had discovered life on the Moon. The first article claimed that he had made these discoveries using a newly designed telescope that was more powerful than any that came before. Later articles described forest and oceans on the Moon, along with bizarre new creatures. Some of the creatures, batlike winged humanoids, appeared to be intelligent, as they were described as building temples.

Needless to say, the whole thing was made up. When readers found out, most were amused rather than upset. And it did cause the Sun to record the highest circulation of any newspaper of the time.

References:
Museum of Hoaxes: The Great Moon Hoax
Wikipedia: Great Moon Hoax