This 1958 sci-fi horror classic tells the story of two high school sweethearts, Steve (Steve McQueen) and Jane (Aneta Corsaut), who see a meteorite drop into the forest outside their rural Pennsylvania town. Out oozes a pink, gelatinous substance, which proves to be a sentient alien lifeform that consumes and absorbs what it touches, growing larger and larger. Steve and Jane try to warn the authorities, but their raving story of an evil blob falls on deaf ears. That is, until the eponymous blob eats so much and grows so large it begins to consume and overwhelm the entire city.
While the idea of a sentient puddle of jelly terrorizing a small town seems outlandish - and, by all definitions, is outlandish - the idea for the classic alien monster flick is rooted in a true story (that is to say, a supposedly true story) that happened one fortuitous night in September 1950. Two Pennsylvania police officers claimed they saw something that looked like a "parachute" or a "sparkly mass" float down from the sky into the woods, and when they went to investigate, they found something truly strange.
Officers Joe Keenan and John Collins claimed in a police report at the time that they found a "purple jelly" substance, 6 feet wide and 1 foot high, that supposedly glowed and was also pulsating. They called for backup and Sergeant Joe Cook took it upon himself to shove his hand in the substance, which clung to his hand before evaporating and leaving behind an "odorless scum." Before long, the entire purple mass had dissipated and dissolved into nothingness.
This bizarre and seemingly impossible report made it to local papers, but likely would have remained a footnote in UFO history if not for movie producer Jack H. Harris, who stumbled across an article about the incident when searching for inspiration for his next monster movie. The rest is history.