In the 1958 film The Blob, a young Steve McQueen and other actors flee from a gelatinous muck that threatens to consume everything in its path. The cult film was remade in 1988 with Kevin Dillon, and both movies overcome a superficially silly premise by making the blob the Michael Myers of sludge—a highly motivated, emotionless entity of pure malevolence.

Surprisingly, the gunk at the center of The Blob was based—at least in part—on a real-life phenomenon.

On September 26, 1950, Philadelphia, Pennsylvania, police officers Joe Keenan and John Collins claimed to have seen something falling from the sky. Searching the area, they found a curious ooze dangling from a telephone pole that seemed to move. When Collins reached out to touch it—apparently, he was not well-versed in the rules of horror movies—it left behind a sticky residue and then simply evaporated. No explanation was ever presented as to the origin of this substance or whether the officers had misinterpreted the situation.

The two did, however, call for back-up, which made for four law enforcement officials corroborating this strange tale.

It became something of a media story, and eight years later, local filmmakers Jack Harris and Irvine H. Millgate mounted The Blob. Though not explicitly based on the 1950 incident, their proximity to it meant they almost certainly would have been aware of it.

Similar cases have been reported over the years, with the strange goo dubbed pwdre ser, Welsh for “the rot of the stars.” Some have attempted to explain the substance as some kind of liquefied meteorite, though that’s not really possible. (Meteorites don’t melt and wouldn’t survive entry into the atmosphere.) It’s more plausible the stuff is just animal regurgitation of some kind. But when one such incident occurred in Scotland in 2009, scientists failed to find any DNA in samples.

The moral of the story? Ideas for movies can be found anywhere. And if you see an unidentifiable blob, remain calm until it starts to chase you.