Slither, a delightfully flimsy horror film.

Michael Rooker and Brenda James in Slither

Not long ago, the only way to make a profitable horror flick was by throwing together some ironically distant teenagers. In the decade since the Scream franchise proved once and for all that scary movies are easy money, pretty much every micro-genre has been revived and strip mined. The filmgoing public has been assaulted by zombies, out-of-retirement slashers, grindhouse-style Slovakian psychos, and phone calls that are coming from inside the house! Until Slither (Universal), though, nobody had bothered to re-animate the particular type of schlocky fare that’s the stock in trade of Troma Entertainment, the micro-budget studio known for gross-out effects and amateur-hour production values.

Before he wrote and directed Slither, James Gunn authored 1996’s Tromeo and Juliet, a farce that merges the Bard’s words with Troma calling cards like lesbianism and decapitation. Still, how can I be so confident that Gunn learned all he needs to know about filmmaking from the trashy studio that brought us The Toxic Avenger? He did co-write a book called All I Need to Know About Filmmaking I Learned From the Toxic Avenger. But beyond that, his latest film bears the hallmarks of a Troma venture: a passel of disfigured and dismembered bodies, and, perhaps by necessity, a refusal to take itself seriously.

Slither opens when an alien egg that looks like a moldy casaba melon falls from the sky and nestles into the South Carolina woods. An unlucky soul named Grant (Michael Rooker) happens upon the downed melon, pokes at it with a stick, and looses a flesh-eating intergalactic slug that jumps inside his chest and short-circuits his brain. Grant’s main symptoms are some unsightly blemishes and a hankering for meat, an urge he satisfies by snacking on the neighborhood pets. When his wife, Starla (Elizabeth Banks), discovers that their basement’s been converted into a slaughterhouse, she suspects that her husband’s in a bad way.

And then comes the slug army, which spews forth from the most horribly distended belly since Monty Python’s The Meaning of Life.  The little buggers start crawling into people’s mouths, eventually turning them into zombies mind-melded to the boss slug that’s controlling Grant, who by this point—follow me here—has grown tentacles and started drooling. (The townspeople suspect he has leprosy or Lyme disease, or might have turned into a giant squid. I thought he looked more like a mucus-covered Noid.) The plot stops for some awkward exposition in which it’s explained that the slugs are a “conscious disease.” The plain-spoken Sheriff Pardy (Nathan Fillion, channeling both Evil Dead’sBruce Campbell and his own gruff space captain from Serenity), prefers not to over-analyze things: “That is some fucked-up shit.”

The sheriff’s got the right idea: This is not a thinking man’s horror movie. I wouldn’t be surprised if there were slugs that could find gaping holes in the plot. But there’s something winning about this grab bag of orally fixated invertebrates and mucus-covered Noids. Compared with a high-gloss, by-the-numbers killfest like Final Destination (2000), Slither looks like the handiwork of a daydreaming middle-schooler goofing off in his backyard. Sure, when the sheriff wrestles an infected deer, it looks more like some badly singed beef teriyaki. But at least the diseased livestock doesn’t look like someone double-clicked it over from OS X. Slither is a drive-in movie for the multiplex age.