[from Wikipedia] The loop of "number nine" featured in the recording fuelled the legend of Paul McCartney's death after it was reported that it sounded like "turn me on, dead man" when played backwards.

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[From Wikipedia] One example of such hidden messages that was prominently cited was in "Stairway to Heaven".[54] The alleged message, which occurs during the middle section of the song ("If there's a bustle in your hedgerow, don't be alarmed now...") when played backward, was purported to contain the Satanic references: "Here's to my sweet Satan / The one whose little path would make me sad whose power is Satan, / He'll give you, he'll give 666 / There was a little tool shed where he made us suffer, sad Satan."[55]

Following the claims made in the television program, California assemblyman Phil Wyman proposed a state law that would require warning labels on records containing backward masking. In April 1982, the Consumer Protection and Toxic Materials Committee of the California State Assembly held a hearing on backward masking in popular music, during which "Stairway to Heaven" was played backward. During the hearing, William Yarroll, a self-described "neuroscientific researcher", claimed that backward messages could be deciphered by the human brain...