In 1936, a church group financed a small morality picture called Tell Your Children. It was meant to frighten parents about a menace called marihuana: one puff and their sons would play piano too fast, their daughters would leap from windows, and everyone would end up in an asylum.

Then an exploitation producer bought it, spliced in racier footage, and sent it around the country under a new name: Reefer Madness.

For decades it vanished. In 1971 a print was rediscovered and screened for laughs, and the midnight movie circuit did the rest. Audiences who had grown up under the film’s warnings watched its piano-pounding hysteria and recognized it for what it was. The scare film became the comedy. The warning became the eponym: to this day, when a moral panic gets ahead of its facts, someone calls it reefer madness.

That reversal is the whole brand. Not the plant. The panic.

The original film is in the public domain, which means anyone can screen it, and everyone eventually does. What is not public domain is what came next: the stage musical, the 2005 movie musical, and the revival that keeps selling out.