“If something exists, there is porn of it:” Welcome to Rule 34, a weekly column in which Motherboard’s Samantha Cole lovingly explores the highly specific fetishes that can be found on the web. If you’ve thought of it, someone’s jerked off to it.

The links, videos and images in this article may be considered NSFW.

There’s a two-and-a-half minute montage of Sigourney Weaver in the film Alien hosted on Pornhub that people are surely getting off to, but it’s just the softcore tip of a hardcore alien sex iceberg.

Alien porn is a lot of things. Sometimes it’s tentacle-based. Other times, it’s about an abduction fantasy. Of course, probing lends itself nicely to the category, and there’s plenty of that. There’s a long mythos of alien abduction and sexual violation: The trope of anal probing during extraterrestrial encounters originated with the first widely-publicized report of an abduction, in 1961. Barney and Betty Hill, a couple from New Hampshire, claimed they were kidnapped by a spaceship. Later, under hypnosis, Barney said he recalled his abductors inserting a cylinder into his anus and taking a sperm sample.

Sex with aliens is a massive genre, falling under “exophilia,” meaning the desire to have intimate relations with non-human life forms. I asked the author and erotic theorist known as Supervert for his insights on alien sex. Supervert has written several books about exophilia—a word he claims to have coined in the 90’s with the writing of Extraterrestrial Sex Fetish.

Extraterrestrial Sex Fetish started a conversation among readers about their deepest desires for alien poon. “Once the book came out, the idea acquired a momentum of its own,” Supervert told me in an email. “People who really did have sexual fantasies about alien life reached out and sent emails. ‘Exophilia’ entered into the lexicon of sexual pathologies. Clearly it tapped into something we didn’t know was there.”

In porn, aliens serve as a convenient variable: an X factor to turn to after all the various life forms on earth are explored and tapped out. Exophilia, he said, speaks to that desire for novelty.

“What could be less attainable than aliens? To lust after them is to adopt a strange attitude.”

On porn tube sites, there are various flavors of exophilia as it relates to aliens—some videos are relatively vanilla, featuring a human having consensual sex with an alien. Others lean into nonconsent and abduction, and then there are tentacle, alien impregnation and ovipositing, and face-hugging subgenres, all of which we’ll get to in a minute.

Enthusiasts have made scads of CGI or traditional animated alien porn, most of which is of questionable quality. It’s the muse of many an illustrator and graphic novelist (see Phil Foglio’s XXXenophile collection) as well as erotic authors (I can personally recommend this collection, simply titled Alien Sex.)

On the more mainstream end, plenty of films deal with alien sex but don’t actually show any alien-on-human interplay. Barbarella, where Jane Fonda fucks her way out of trouble on a distant world and My Stepmother is an Alien starring Kim Basinger as an extraterrestrial undercover on Earth are two classic examples.

Many, many tentacle-based porn videos are also alien porn, and this is its own, massive fetish category. But it’s often difficult to suss out whether we’re talking about aliens with tentacles or sea creatures (although there are some fun theories out there about octopuses arriving from other planets).

But at its most basic form, Alien porn is simply about getting it on with an alien. Kristal Summers’s performance alongside an unknown actor in a plastic mask that looks like it came from a Spirit Halloween store is perhaps the most minimalistic example I could find of this. Summer is tied up and ravaged by the most stereotypical alien-looking creature one can imagine.

But you don’t need another person in the room to get your intergalactic freak on. Fetish model Reiinapop’s “Alien Sex Bath” is a glittery, space-themed, solo clip for fantasizing about watching an interstellar babe take a bath.

Then there’s the ovipositor crowd. Scientifically, an ovipositor is a tubular organ on female insects or fish, used for depositing eggs. As a fetish, this means using a dildo with a divet in the ends, for placing a disintegratable, jelly egg for insertion into the orifice of your choice. Maren Hill demonstrates this as the “willing host” in a video featuring abduction and impregnation.

“Many like to envision an alien creature that wants its eggs inside you,” LoneWolf, the owner of Primal Hardwere and patent-holder for the official Ovipositor, told VICE in August. “It can be a little intimidating or off-putting to those who do not fantasize about being the willing or unwilling host of alien beings inside them. It blurs the line of our own humanity to find sexual pleasure with something that is so far from human, and for some, just talking about it gets them wet.”

Like tentacles and alien impregnation, face huggers make up their own, extensive category of porn. The origins of face hugger porn—where an alien creature latches onto (usually) a woman’s head and fucks her face—are unclear to me at this time, but I can only assume that people watched Alien and thought it would be hot to watch someone get attacked by a face hugger.

YouTube is also home to quite a bit of alien porn. Notably for our alien-on-human purposes, there’s “E.T. 2” by YouTuber FilthyFrank, which imagines if ET came back to earth ready to party. Like with Lego porn, it’s occasionally difficult to differentiate between serious fetish-attainment works, and alien sex for comedic purposes, but this one is probably the latter. Although, the sex scene clipped out alone has over a million views, so who can say.

All of this speaks to something inherent in desire itself: Longing for the unattainable.

“What could be less attainable than aliens? To lust after them is to adopt a strange attitude,” Supervert said. “Instead of projecting his desire onto an individual, who could cause frustration and pain, the exophile projects it onto a being he knows does not exist. He acknowledges the lack at desire’s heart but simultaneously gives it a face or a dozen arms like a Hindu deity. If it sounds dream-like, with its contradictory levels of awareness and fantastic distortions of form, then we know exactly what Freud would have said about it. Wish fulfillment.”

This content was originally published here.