If the thought of characters breaking into song doesn't bum you out, and if you have an appreciation for parody and dark comedy, then you'll have a high time watching "Reefer Madness" (8 p.m. tomorrow, Showtime), a movie musical version of the stage show that premiered in Los Angeles in 1999.

		'Reefer Madness' When: 8 p.m. Saturday on Showtime

That production was based on the late-1930s propaganda film "Tell Your Children" (later retitled "Reefer Madness"), produced by a church group to warn parents of the dangers of marijuana to the youth of America.

Written by Dan Studney and Kevin Murphy, now a writer on "Desperate Housewives," the new movie musical is an irreverent spoof of that original film and hews pretty closely to its plot, at least until the last 30 minutes.

It begins in black and white in 1936 as a lecturer (Alan Cumming, who plays a variety of roles) screens an anti-marijuana film for the parents of high school students. On the perils of pot, he sings, "Creeping like a communist, it's knocking at our doors, turning all our children into hooligans and whores."

Once the lecturer turns on his projector, the film shifts to color for the story of cherub-cheeked 16-year-old Jimmy Harper (Christian Campbell), a wholesome teen with a virginal girlfriend, Mary Lane (Kristen Bell, "Veronica Mars"). They hold hands, share sodas and daydream of their wedding day.

But their blissful innocence gets torn apart when Jimmy falls in with a bad crowd (led by Steven Weber and Ana Gasteyer) and becomes addicted to the wacky weed. Singing, dancing and simulated pot-smoking ensue.

"Reefer Madness" is a lavish period production complete with 16 musical numbers. At 110 minutes, it does start to feel a little long after a while, but just as I started to lose interest, along came another creatively choreographed song with smart, funny lyrics to keep my attention. It's tough to knock a film that manages to rhyme "transubstantiate" in song.

But I'm sure some people can and will be offended by "Reefer Madness," which features Jimmy having a pot-induced vision of Jesus Christ (Robert Torti), who warns him to reform his ways, singing, "Listen to Jesus, Jimmy, I'm the poster boy for Easter."

You don't have to be a pot proponent to appreciate the charms of "Reefer Madness," which is actually more a spoof of the original propaganda film and the paranoia it attempted to inspire. The concluding scene also includes a nod to current events as Cumming sings, "When danger's near, exploit their fear."

Despite Showtime's insistence that "Reefer Madness" is "a feel-good" musical, it actually falls more in line with darker fare ("Little Shop of Horrors," "Batboy: The Musical") as it mixes mayhem with comedy, but the entire cast, several of whom starred in stage versions of the show, keeps the tone buoyant, even when characters are drenched in blood.

Kudos especially to Cumming, whose characters act as the story's narrators, and Campbell and Bell, both of whom start out as impossibly cute and fresh-scrubbed and later transform themselves into slaves to the weed. Though "Reefer Madness" is intended as raucous satire, their performances have such gusto that you can't help but love them.