When an alien from another planet, whether one of the Little Green Men or one of The Greys or whatever, kidnaps a human (often by way of Tractor Beam). The alien generally leaves no trace of the human until it's done with it. Alien abductions do get witnessed, but the witnesses are almost always portrayed as a bit mad even when the alien abduction is real in canon.
Humans returned from alien abductions usually have had bad things happen to them. They may have had a complete physical, possibly without anesthesia. They may have a little tracker planted in them. They were most certainly probed and violated though. And even a benign alien can cause an abduction, and cause problems, if Time Travel in either direction happens. Or they have been forced to be The Chosen One.
Sometimes, if the alien is benign, the human will witness something that makes the abduction worth the trouble. If the aliens' interest is scientific research, expect them to be terrible at it: No Control Group, no reliable tranquilizers (because how else could abductees keep waking up too soon, so they can see they're in a spaceship?), and no acknowledgment that it's indiscreet to keep abducting idiots who'll rush to spill their story to the tabloids.
Malevolent aliens don't always bother to return the human. There might not be anything to return.
Before aliens from outer space became a popular concept, literature and folklore used fairy abductions, demon abductions, and gods abducting fair maidens. Many of these stories reflect sexual urges excused and resolved through the agency of an irresistible entity like a god or alien.
- The Skrulls, a shapeshifting alien race who are primarily Fantastic Four villains, are in the habit of abducting humans in order to replace them for espionage purposes (at first because Earth was strategically located in their Forever War with the rival Kree Empire, later because they've managed to make enemies of Earth's many superheroes). They normally keep their victims alive just in case they might be useful in the future.
- The backstory of Cyclops of the X-Men has his parents being abducted by Shi'Ar Emperor D'Ken, who seemingly just picked them at random because he's nuts. His father survived captivity and eventually became the Space Pirate Corsair.
- Invasion!: The Dominators abduct humans to experiment with the meta-gene, and the shapeshifting Durlans abduct humans to imitate and replace them.
- Superboy (1994): Kon-El, Dr. Sterling Roquette and a couple other Cadmus personnel get abducted and enslaved by the extraterrestrial slaver Kossak while Cadmus is trying to decipher the workings of a small space craft revealed to have been stolen from Kossak by an escaping slave before it crashed on earth.
- Wonder Woman (1987): Wonder Woman and Natasha are abducted by the Sangtee Empire. In a twist they were already in Sangtee Empire space when this occurred due to malfunctioning New Genisis tech that had been modified for a hasty rescue mission from a simple space station orbiting earth.
- Calvin has used this as an excuse several times in Calvin and Hobbes; once he said that aliens came and drained all the math from his brain, while another time aliens arrive and replace him with an amoral robot duplicate (his mom was less than impressed by the story).
- Pedro from The Wacky Adventures of Pedro frequently gets captured by aliens.
- Garfield: Garfield is worried about his girlfriend Arlene because she believed his alien abduction excuse.
- One Herman strip shows a man with a tracking collar and ear-tag yelling about "ALIENS!"
- In The Conversion Bureau: Cold War, Xenolestia is responsible for over 2,000 Chinese citizens being kidnapped and forcibly turned into newfoals.
- In The Simpsons fanfic Must Love Ned Flanders, one of the "deleted scenes" mentions Kang and Kodos (aliens) abducting the Simpsons.
- In Worldwar: War of Equals, the astronauts aboard the ISS are taken prisoner after The Race board the station two days before they invade. When the actual fighting starts, the capture 20,000 Egyptian soldiers after Cairo is overrun by Race forces. Later starts to be inverted when we start capturing Race personnel.
- Inverted in Daft Punk's long-form anime music video, Interstella 5555: The main characters are aliens who are kidnapped by an Earthling entertainment mogul to make pop music as part of convoluted plot for intergalactic domination, which means that, despite the inversion, it technically still is an alien abduction.
- Subverted in Happy Feet, when the skua tells young Mumble of his alien abduction.
- Jazz musician Sun Ra claimed he was abducted by aliens and originated from the planet Saturn, a theme he elaborated futher on in his stage shows and albums.
- In "Weird Al" Yankovic's "Everything You Know Is Wrong", the narrator accidentally walks into an alternate dimension and gets abducted by aliens who all look like Jamie Farr. They remove his internal organs and take pictures of them, then thank him for being so cooperative during the whole ordeal and offer to send him back in time to any point in history he wants. He chooses to go back to the previous Thursday night so he can pay his phone bill on time.
- Spanish neoclassical metal band Dark Moor has a song which is all about this, appropriately titled "Abduction".
- Journey into Space: In The Red Planet, the Martians have abducted many humans from Earth since at least 1879. The abductees include Bill Webster (who was taken in 1910), James Edward Whitaker (who was taken in 1924), John and Martha Bodie and a dingo hunter (who were taken in 1939) and the flying doctor (who was taken in 1956).
- Changeling: The Lost, being about The Fair Folk and their victims, emphasizes the ties between Alien Abduction and the old faerie myths — some Keepers are described as androgynous, slender beings that put their victims through strange examinations involving horrifying equipment, and the Wizened in the illustrations appear to be a mixture of traditional goblins and The Greys. Of course, the book goes on to say in a sidebar that not all alien abductions in the World of Darkness may be the fault of The Fair Folk....
- In the world of Pathfinder, hapless people sometimes disappear from their homes, only to reappear sometime later with mysterious surgical scars and no recollection of what happened beyond vague nightmares of short gray-skinned creatures with bulging eyes... except instead of aliens from outer space, they've been abducted by derros, fey-like humanoids from Beneath the Earth. A Shout-Out to the literature of Richard Sharpe Shaver and his "deros", which may have inspired the idea of The Grays in the first place.
- Karate Bears were abducted once.
- In Alien Dice, Chel, who's about to board a spaceship voluntarily, wonders for a moment if aliens abduct you by talking you into coming with them. Later it's revealed that humans were abducted in the past to create the Rishans but it was forbidden by the laws of The Federation.
- I Was Kidnapped by Lesbian Pirates from Outer Space. It's the title.
- Happens a lot to Denver in Starfire Agency, and they never return him in the right clothes. Turns out he's a slightly damaged replicant created by the Greys.
- In Bob and George, this does not keep George's home dimension from dullness.
- In Red's Planet, Red is abducted. So are many other aliens, from other planets. Then they crash land.
- In Allen the Alien, the beginning of the plot is Allen, actually a human, getting abducted thanks to being drunk.
- Happens to Alice. She gets very excited about it, though she momentarily references Anal Probing — though the aliens tell her they don't do that anymore.
- In Cool Cat Studio, an abduction marks the point where the comic jumps from Slice of Life to high weirdness.
- Part of the premise in Trying Human is that The Greys are conducting an extensive research program, abducting humans on a precise schedule. The other part of the premise is Interspecies Romance, and lots of it.
- Inverted in Abductee◊ by Glennz.
- Inverted even more consequent by cartoonist Neil Bennett.
- According to Tlf Travel Alerts this is the inevitable result of using the Dockland's Light Railway. Expect delays.
- In The Jenkinsverse, The Corti do this to all pre-FTL species so as to learn everything they need to sell advanced pharmaceuticals, cybernetic implants and other wonders to them. Most of the human protagonists in the J Verse were abductees at some point.
- The concept has proven to be good fodder for ASMR videos.
- Probably the most famous alleged alien abduction case was that of Betty and Barney Hill, a married couple who claimed to have been abducted by aliens in rural New Hampshire in 1961. Their claims were investigated by the government and media, and it became the Trope Codifier for alien abduction stories. Betty passed a lie detector test, and both she and her husband stuck by their claims till death.
- One of the most unusual alien abduction stories was that of American logger Travis Walton. Walton was allegedly abducted by a UFO in Arizona in 1975. His abduction was reported by several coworkers who claimed to have witnessed the event, resulting in a state-wide manhunt (and a possible homicide investigation). Walton did not reappear until five days later, claiming he had been abducted by aliens. The movie Fire in the Sky is very loosely based on the alleged abduction.
- Scientist/cultural analyst Jacques Vallee once investigated an abduction very similar to Travis' which had happened near his home town in France. He discovered it had been staged by the French equivalent of the CIA as a social experiment. He thinks this has happened more than once, and is not connected only to government agencies. He also believes there are real UFO sightings and "aliens", but they are not from outer space but are "multidimensional across space and time". Vallee inspired the character of Claude Lacombe in Close Encounters of the Third Kind.
- Wild animals captured by humans, examined and tagged, then released again. From their perspective this trope might be close to Truth in Television. One The Far Side strip uses this very setup, as does the film Happy Feet.
- A widely accepted theory for why people have such vivid memories of alien abductions is because of a phenomenon that's basically "dreaming while awake". When you dream, not only do you have very strange and surreal images, but your body actually shuts down most muscles so you can't move and accidentally hurt yourself. Sometimes you can "wake up" — i.e. your eyes open and you're aware of the room you're in. So imagine; you wake up. You can't move your body. You're dreaming of strange lights. It fits all the tropes of alien abduction, further influencing your dream, and you become convinced it actually happened. This is why it's called "sleep paralysis". It can also lead to dreams of ghosts and other paranormal/supernatural beings. A common account was once of a "crushing hag" sitting on the person's chest, crushing them-hence the term "hag-ridden" for one plagued by nightmares. Demons that sucked people's breath away, or abused them sexually (familiar to UFO abduction) were prevalent in Medieval Europe. With multiple people, misidentification of natural phenomenon, hallucinations, and outright fraud are often proven behind many alien abduction stories. Use of hypnosis (as both the Hill and Walton cases featured, above) has also been found to implant memories easily by the hypnotist (accidentally usually), making these suspect at best without some independent evidence (which is generally lacking).