Marijuana, according to the opening credits in the 1936 propaganda film Reefer Madness, is An Unspeakable Scourge! The Real Public Enemy Number One!

Originally titled Tell Your Children, the movie is a cautionary tale about wholesome high schoolers who turn into raving maniacs — cackling uncontrollably, dancing an uninhibited Charleston and giving into to their basest urges — after just one puff of the demon weed.

Certainly there are some who still think this is what happens, although science has proved otherwise. Seventy-seven years ago, however,Reefer Madness was some scary-ass shit in the era of Herbert Hoover and FDR.

Over time the campy, deliberately over-the top film became a cult classic, beloved by potheads who find its unintentional humor illuminating, and funny enough to bust a gut over.

Bay Street Theatre's production of the 1998 musical take on Reefer Madness opens this week, and if you need any more evidence that times have indeed changed, consider this: The rights to the musical are held and administered by Rodgers and Hammerstein Theatricals, Inc.

The Kevin Murphy/Dan Studney musical satire features most of the characters from the 1936 film, including clean-cut Jimmy, sweet and innocent Mary, drug-pushing scumbucket Jack and den-of-iniquity mistress Mae.

Director Timothy Reynolds says Reefer Madness shares DNA with other campy, over-the-top musicals like The Rocky Horror Show, Avenue Q and even Cabaret.

In short, perfect for Bay Street Theatre.

"It's theater of the ridiculous," Reynolds explains. "The spirit of the movie is still there. People still smoke weed and immediately become addicted, and live debaucherous lives of sin and killing each other. All the classic musical values."

Even Jesus Christ has a show-stopping number in this morality tale turned upside down. There's a character called Goat Man.

It's straight-down-the-line satire.

"What I like about the play so much is that it makes the point that it's not madness caused by reefer, but it's madness caused by trying to control it," says Reynolds. "Trying to contain it.

"It's a remarkably clever show. It still has all the campy elements of the original film, but it's definitely got its own wit and sense of humor about it. And it doesn't take itself too seriously."

The cast includes Gia Erichson as "The Lecturer," Leonard Rose as Jimmy, Samantha Binkerd as Mary, Matthew Ryan Gunnells as Jack, Valerie America Lavelle as Mae, Donald Jarvis as Ralph and Cecilia Arango as Sally. There is a live band.

Murphy and Studney created their Reefer Madness as a play-within-a-play, a fourth wall-breaker that gives the audience a frequent nod and wink. "They can't help but draw on that," Reynolds explains, "but a lot of the jokes are just playing on the sense of theater of it. The speed of the costume changes. The guy that's playing Jack the Drug Dealer is the same guy who's playing Jesus Christ. That's the subversive sense of humor of it."

There is, of course, rampant (simulated) drug use, sudden violence, bad Charleston dancing and scantily-clad "sex" scenes. "Things are humped, because the story demands it," Reynolds laughs. "I wouldn't have done it otherwise."

(The director suggests leaving the kids at home for this one, even the "all ages" Sunday performances.)

Rehearsals have been a hoot, with the cast laughing almost as much as hopheads Jimmy, Mary, Ralph and the gang did on the screen in 1936.

"It's not like a movie where you go 'Let's explore the backgrounds of the characters,'" says Reynolds. "The characters are devices to get the point across.

"Everyone just dove straight into it, sunk their teeth into it — whatever metaphor you'd like to use — they went into it with full force and vigor."