Had the 1990 creature feature Tremors been given carte blanche to be as gross and disgusting as it wanted to be, it probably would've looked a lot like Slither. In an age when numerous horror films are sacrificing their content in order to score an accessible "PG-13" rating, Slither welcomes its "rated R" branding with open arms, seizing the opportunity to push the envelope and get as downright icky as it can get. But Slither isn't all guts and no glory; this film is as gross as can be, but it doesn't forget to be an entertaining ride nor to incorporate wry undertones that put the movie a step above those pale wannabes giving the horror genre a bad name.

In the small, sleepy town of Wheelsy, where the most fun thing residents can think of doing is dancing with fake deer antlers at the bar, something sinister is about to take place. A rock from the farthest reaches of outer space has crash-landed in town and quickly goes about enacting its evil plans, starting by infecting the wealthy Grant Grant (Michael Rooker) with an alien creature -- a thing that starts transforming him into a being you might get if you threw Michael Rooker, a squid, and some chewed-up gum in a blender.

Pets are found torn to shreds and people disappear, with all signs pointing to Grant as the culprit. But Chief of Police Bill Pardy (Nathan Fillion) and his deputies soon uncover a plot that goes far beyond the deaths of a few family dogs. The possessed Grant has become the catalyst for a full-scale alien invasion, sending slimy little space slugs to burrow their way into peoples' brains and turn them into obedient zombies. It's up to a small group of survivors, including Pardy and Grant's wife Starla (Elizabeth Banks), to put an end to the attack before it spreads even further.

It seems fitting that Slither begins with an old-timey horror movie score, in the vein of golden-age shockers like Frankenstein and The Wolf Man, since the studio distributing the film, Universal, once ruled the roost as Hollywood's king of fright flicks. If Universal is set on ushering in a new era of horror films to match its output from the '30s and '40s, then Slither isn't a bad place to start.

Instead of setting his sights on just one realm of horror, writer/director James Gunn (who penned 2004's unexpectedly excellent Dawn of the Dead remake) throws numerous genre ingredients into his story. Monsters, zombies, and space worms (oh my!) all converge for a veritable buffet, with the citizens of Wheelsy as the main dish. Gunn is the maestro behind the scenes, blessing the film with a polished look but a free-spirited attitude toward horror. He brings an insane energy to the proceedings, doing more than just showing a bunch of disgusting set pieces one after the other. Instead, he gives such scenes backbone in the form of likable characters and a good dose of dark humor. There are also a couple of moments where Gunn slides in a little commentary on the nature of mankind, using the story as a means of showing what would happen if Man's dominance were taken over by a much fiercer life form. 

The key to Slither's success is that it never gets too serious but never becomes overly goofy either, opting to go with an approach in which the characters share a collectively funny "What the..." reaction to every gross-out sight they stumble upon (be it a zombified deer attack or a woman giving birth to a slew of slugs in a most unfortunate and painful way).

Fillion (of the doomed TV show "Firefly" and its cult hit spinoff film Serenity) makes a fun, wisecracking hero. Banks does good work as a woman who holds onto the idea of marriage as a sacred bond, even though her husband is starting to look like a wad of Silly Putty wrapped in used flypaper, and Gregg Henry stands out as the movie's most riotous character, the town's weaselly, profanity-spewing mayor. 

Unfortunately, not many of the other characters get to be as interesting, since they either wind up as slug bait, are thrust into hero roles on a moment's notice, or, in the case of the talented but underused Michael Rooker, spend so much time encased in make-up that the actor is left fighting to convey his own traits and mannerisms to the audience. Slither as a whole comes off in much the same manner. Although packed with as much slime, gore, and creepy-crawly creatures as a horror fan could ask for, it's not as memorable as one would hope, especially considering the many high points it contains.  

Still, Slither's job is to entertain its audience while reveling in its own sickening glory, and that's a job filmmaker Gunn pulls off exceptionally well.

WARNING: If you're going to bring a lunch to Slither, prepare to lose it.

MY RATING: *** (out of ****)

(Released by Universal Pictures and rated "R" for strong horror violence and gore, and language.)