I would say sleep paralysis, here's an article on it.
Sleep Paralysis Information
There are people out there who claim to have been abducted by aliens. They describe these aliens as short with a frail body, big head, large black eyes, gray skin necked and with no visible genitalia. They say these aliens experiment on them and even molest them for purposes of creating hybrids.
Most people who claim to have been abducted sincerely believe what they are saying but beyond the story’s, there is no evidence for it and when you really think about it, there are logical problems with the story’s.
First off, the aliens them self’s; large head and week body are indicative of a low gravity, in fact such body’s could not survive in earths gravity, they would not have enough mussels in there necks to support there heads and there body (though they could survive for a short time) would be too frail to survive in earths gravity. And there body’s don’t make sense, they have large eyes indicative of a low light environment but a low light environment would be cold and they lack the fer and blubber that a creature that evolved in a cold environment would have.
And then there’s the problem that there humanoid. We evolved our body structure cause of the body structures of our ancestors and the conditions that drove there evolution. Given all the possible environments and body structures the chances that another humanoid species would evolve are slim.
Another problem is physics. The speed of light is only 299,792,458 metres per second (186,282.397 miles per second) and the closes star is 4 light years away. You can’t go faster than light, its not a matter of “we don’t know how” its a impossibility.
Yes there are hypothesise on how to get around the speed of light problem, you could make a worm whole but unlike what science fiction tell you, a worm would be 2 connected black wholes. And there the Alcubierre drive (warp drive) but that would have allot of problems and require the energy of 5 suns. Any aliens visiting earth would be limited by the speed of light.
Sure they could get here at speeds less then the speed of light hell if they traveled at near the speed of light the time dilation would mean it would be months to days to even minuets for them to get here (in there perspective, in the rest of the universe years would have passed) but that would have required allot of energy to accelerating to those speeds and decelerate from them and you would have to add in the time needed to accelerate and decelerate. And why would they come all that way just to experiment on us?
Historically, there have been story’s of monsters that molest people at night, like story’s of incubuses and succubus’s and even story’s of people being kidnapped in there sleep at night and takes to some place and then brought back to there bed.
People use to believe those things happened to them. Couldn’t these gray aliens are just our modern demons?
During the 80’s there was allot of fear of “Satanic ritual abuse”, there where many who claims to have been abused in satanic rituals and believed they where had even had memory’s of the abuse but the investigations into the abuse found nothing, no evidence of these “satanic” groups, and evidence of the abuse.
On top of that most of the people who call them self’s “satanists” don’t believe in God or the devil (they use Satan as a symbol of rebellion) and those who do believe in the supernatural bing called Satan, its not the Christan Satan. And none of them practice the rituals that where alleged to have taken place.
There there are things we know that shed allot of doubt on alien abduction.
Sleep paralysis is a condition that some people have, people with sleep paralysis sometimes when they wake up they don’t wake up completely, they are still partly asleep and dreaming. When people dream there body temporally paralyses it self so people don’t act out there dreams, so when they wake up and are still dreaming they can’t move. And then they see things that are not there cause there still dreaming.
People who believe them self’s to have been abducted by aliens often “uncover” these memory’s in hypnoses. People use to think hypnoses was some magical window into the mind, well its not.
Hypnoses has been known to and can easy create false memory’s, the person doing the hypnoses can easy influence the patent into forming false memory even when they do not realise they are doing it (they could think there doing everything right but are in fact influencing there patent into forming false memory’s). And the patents own preconceptions can form false memory’s under hypnoses, for insistence a person believes that he has been abducted by aliens goes to be hypnotised to uncover these memory’s, the memory don’t exist but his belief and state of hypnoses form these false memory’s.
When dealing with alien abduction we should use Occam Razor (one should not increase, beyond what is necessary, the number of entities required to explain anything), there is a simple explanation for the phenomenon. Sleep paralysis, hypnoses or a combination of the 2 explains it perfectly and with out the improbability’s of improbable aliens (there body structure, not the existence of extraterrestrial life)) visiting earth.
wolfsden.wordpress.com/2008/0...ien-abduction/ 
