Fear of infection, of contamination, of losing your personhood, of physical violation—all of it coalesces in often gooey fashion in the parasite movie. Metaphors abound and slugs take center stage as some of the greatest directors of the genre tell the tale of hosts and unwanted guests. Here are our favorites.

Shivers (1975)

In an upscale Montreal high rise, an epidemic is breaking out. A scientist has created an aphrodisiac in the form of a big, nasty slug. That slug, though, spreads wantonness throughout the high rise and threatens to overrun the city with its lusty ways.

Shivers takes a zombie concept and uses it to pervert expectations. (See what we did there?) Cronenberg’s his first feature length horror predicts so many of the films to come. The film obsesses over human sexuality, social mores, the physical form, physical violation and infestation, medical science, conspiracy, and free will.

Splinter (2008)

Road kill, a carjacking, an abandoned gas station, some quills – it doesn’t take much for first time feature filmmaker and longtime visual effects master Toby Wilkins to get under your skin. One cute couple just kind of wants to camp in Oklahoma’s ancient forest (which can never be a good idea, really). Too bad a couple of ne’er-do-wells needs their car. Then a flat (what was that – a porcupine? No!!) sends them to that creepy gas station, and all hell breaks loose.

Contamination gymnastics call to mind the great John Carpenter flick The Thing, but Splinter is its own animal. Characters have depth and arcs, the danger is palpable, the kills pretty amazing, and the overall aesthetic of that old highway gives everything a desperately lonesome quality where you believe anything could happen and no rescue is in sight.

Slither (2006)

Writer/director James Gunn took the best parts of B-movie Night of the Creeps and Cronenberg’s They Came from Within, mashing the pieces into the exquisitely funny, gross and terrifying Slither.

Cutie pie Starla (Elizabeth Banks) is having some marital problems. Her husband Grant (the great Michael Rooker) is at the epicenter of an alien invasion. Smalltown sheriff Bill Pardy (every nerd girl’s imaginary boyfriend Nathan Fillion) tries to set things straight as a giant mucous ball, a balloonlike womb-woman, a squid monster, projectile vomit, zombies, and loads and loads of slugs keep the action really hopping.

Consistently funny, cleverly written, well-paced, tense and scary and gross—Slither has it all. Watch it. Do it!

The Thing (1982)

John Carpenter’s remake of the 1951 SciFi flick The Thing from Another World is both reverent and barrier-breaking, limiting the original’s Cold War paranoia, and concocting a thoroughly spectacular tale of icy isolation, contamination, and mutation.

A beard-tastic cast portrays a team of scientists on expedition in the Arctic who take in a dog. The dog is not a dog, though. Not really. And soon, in an isolated wasteland with barely enough interior room to hold all the facial hair, folks are getting jumpy because there’s no knowing who’s not really himself anymore.

This is an amped up body snatcher movie benefitting from some of Carpenter’s most cinema-fluent and crafty direction: wide shots when we need to see the vastness of the unruly wilds; tight shots to remind us of the close quarters with parasitic death inside.

Alien (1979)

After a vagina-hand-sucker-monster attaches itself to your face, it gestates inside you, then tears through your innards. Then it grows exponentially, hides a second set of teeth, and bleeds acid. How much cooler could this possibly be?

Much ado has been made, rightfully so, of the John Hurt Chest Explosion (we loved their early work, before they went commercial). But Ridley Scott’s lingering camera leaves unsettling impressions in far simpler ways, starting with the shot of all those eggs.