You've probably heard of alligators terrorizing city sewers. These rambunctious reptiles supposedly start their lives as babies taken home from pet shops or carnivals, flushed when fickle kiddies tire of the critters, and grow to monster-movie proportions underground. Could this be true?

Actually, no.

Jan Harold Brunvand is an urban-legend expert who has spent decades tracking down the fables that folks in America and around the world share. Most of the tales that have reached his ears prove to be false—and this one is no exception. He says the events in question usually happen to a “FOAF”—a friend of a friend. The supposed close connection to the tale teller lends credence to the yarn, but because the person is not actually named, the story can't be confirmed. Other famed legends center around overzealous tanners cooking their internal organs with ultraviolet rays (not possible), and green M&Ms making people feel randy (no comment).

According to Brunvand, the alligator myth has been circulating in various forms since 1935, when the New York Times reported that a full-grown alligator was dragged out of a city sewer. No one knows how the gator got down there, but that one recorded instance of a sewer-dwelling reptile more than 70 years ago has turned into an oft-repeated tale of mythic proportions—the best-known American urban legend on record.

To learn more about this and other urban legends, pick up Brunvand's comprehensive Encyclopedia of Urban Legends from your favorite online or real-world bookstore.