TIME has a fascinating account of the 10 biggest pranks in geek history. This one is the infamous Hollywood sign prank, perpetrated by (who else?) Caltech students:
During Hollywood's centennial in 2003, Caltech's Prank Club tackled the famous Hollywood sign with cherry pickers, large sheets of black and white plastic, and duct tape. They hung just enough plastic so that from a distance, the sign appeared to read "Caltech." "Hollywood is still mad about that," says Autumn Looijen, author of the prank history, Legends of Caltech III: Techer In the Dark. The sign assailants' names never surfaced, but their work has become famous on campus. (Both Caltech and MIT tout their students' pranks on their admissions websites.)
http://articles.latimes.com/1987-05-19/local/me-1219_1
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