Something in 'Slither' slithersCasual horror fans may experience several instances of discomfort watching James Gunn's "Slither," queasy moments involving orifice-penetrating leaches, orifice-violating tentacles and orifice-esque alien pods. For genre aficionados, seeing "Slither" will be like sliding into a comfortable easy chair. Gunn's directorial debut pays homage to so many classics with ample enough wit that most viewers won't care that "Slither" doesn't offer much originality of its own.

The film begins at the start of deer season in tiny Wheelsy, a community composed mostly of rednecks, has-beens and never-weres. The town's big fish is Grant Grant (Michael Rooker), a businessman with a big house and a beautiful wife (Elizabeth Banks). Things are about to change in Wheelsy. After a physical encounter with an extraterrestrial blob of goo in the woods, Grant begins to change. At first, it's just an enhanced sexual appetite and a hunger for meat, but soon he's developing unusual body modifications and a desire to spread his mutated seed. What follows is squishy, funny and plenty entertaining, as Grant's alterations draw the attention of the town sheriff (Nathan Fillion), the mayor (Gregg Henry) and several other disposable characters.

The film's tone -- a mixture of uncomfortable violence and disarming humor -- owes a lot to the work of Frank Henenlotter ("Basket Case"), Stuart Gordon ("Re-Animator"), Sam Raimi ("Evil Dead"), early Peter Jackson ("Dead Alive"), George Romero ("Dawn of the Dead") and John Carpenter ("The Thing"), as well as to comedy-horror landmarks like "Tremors." Mostly, "Slither" owes nearly everything to the early work of David Cronenberg, lifting chunks of the dark gory satires "The Brood" and "Rabid." The "Slither" moneyshot -- a cute girl in a bathtub unaware of the squirmy critter aiming at her vulnerable bits -- is a direct lift, in fact, from Cronenberg's "Shivers." Going back even further, "Slither" also harkens to the old Universal horror films in which the monsters were sympathetically driven by love for the heroine.

Although it looks proudly low budget, "Slither" uses a combination of practical effects and CG to generate the necessary visceral reactions. The glistening leaches are far and away the most successful invention, which explains why they're the centerpiece of the movie's promotion despite the fact that only appear in a couple isolated scenes.

Nearly as important are the game cast members, particularly Fillion and Henry. "Firefly" fans have long embraced Fillion's ability to infuse any dialogue, however incidental, with deadpan quirk. Henry, best known for telling poor Rory she wasn't cut out for journalism on "Gilmore Girls," takes the opposite approach, barking out his lines with a manic absurdity. It's impossible to figure how many laugh-generating punchlines work only because of the delivery.

Gunn's inexperience is evident in both the flat staging of some scenes and in the meandering and unfocused plot. Bouncing all over the map, "Slither" doesn't build any tension as a zombie movie, a creature feature or as a sci-fi creepfest and the lack of a throughline make it a series of enjoyable bits, rather than a satisfying whole.