Its not just the greys, but other species of aliens are a lil freaky as well. The near-humanoids such as the Nordics are known to play around as they are the most familiar. Reptilians as well are known for their sensuality. Greys are weird in the sense they often collect sample for hybrids....and they have a cloaca it seems. People often don't want to talk about sexual intercourse and aliens, as most people have traumatic experiences as these are non-consensual. However, there have been cases where it was consensual and pleasurable for all. Keep in mind when we are discussing sex with aliens, this is an inter-species experience.
Nordic
These near-humanoid aliens often appear as tall fair skinned blonde and blue beings. There are some variations that differing in height, meaning that they can be comparable to standard human height to extremely tall as in 8' plus. Other variations may have pointed ears or slanted eyes, with some blending in classic "grey" anatomy such as a large cranium and eyes, along with a different type of skin. In general the Nordic type apparently originates from Pleiades, but other near human types claim to be from elsewhere such as our inner earth known as Agartha. The most famous such individual is Valiant Thor, an ambassador from "Venus" who came to help the U.S. in WWII. Ironically over in Germany at that time, another Aryan variant known as the Vrill were helping the Axis powers. There are tales of other near human like aliens such as the Annunaki from ancient Mesopotamia and Nephalem in our bible.
Sexual relation with theses beings is easy....as they appear to be mammals with compatible sexual organs. They also seem to have a heightened energy that is pleasurable to humans....as most encounter are considered consensual (borderline manipulated) as they are very attractive and alluring.
Grey/Eben
The infamous greys shown first above come in variety of skin tones, ranging from blue, grey, white, almond, golden yellow, and brown. Most appear short and lithe, ranging from 3 to 5 feet in height. They often have large heads with large dark eyes. Some have eyelids and some don't. The color of there eyes are also all black, indigo with specks of silver or white, are have very large colorful iris with black sclera. They have anywhere from 3 to five long fingers or toes and often wear no clothes. Others tend to favor robes or skin tight jumpsuits. There are other types of greys known as the "Tall Whites" which are 6 to 8 feet in height and thinner. Any of these can also have a mixture of other features that indicate an insect-like relations such as faceted eyes, mandibles, and antennae. Some seem piscatorial in nature with nubs on their heads like seahorses and have a cloaca. They appear not to have a sex or gender as we know it, and some seem gender fluid or neutral. Their skin texture also feel much like a dolphin or other cetacean, but also like the chitin of many aquatic species.
Greys are not mammals, and are most notable known for work in hybridization...as they have made a number of chimera, human and "grey" type experiments. I wouldn't not call they hybrids, as our mammalian DNA does not seem compatible.... and given the overall experiments and they have done....it just looks like gene-modification on their part by redesigning our human embryos with aspects of their genetics or traits.
Sexual relations with them are interesting because the do not appear to have genitalia or anus. They do have an oral orifice and nasal cavities. The cloaca could serve as collection organ for sperm, but both male and female humans claim to have sexual encounters. They are known for using tools in regards to sex, but approach it in a clinical manner for copulation to produce embryos. If anything many often will find a male human and female human with compatible traits and force them to mate. These beings are usually manipulated to do so while the greys look on.
Another form of sexual activity some Greys are involved in are part of the CE4-1 and CE4-2 variety, as they are mental constructs in the form of lucid dreams. Here actual attempts of "love" making can be done without the physical limitations of our differing biologies. Here they often appear as people we know or fantasize about, yet rarely the illusion falls apart when behaviors come to play. The illusionary partner will behave differently or they choose some inappropriate for an intimate connection.
Energy Being
These beings have transcended their physical forms and limitations an exist as beings of light or "energy". They claim to be free from the temptations of flesh, but have an interest in us "dense and fleshy forms" for purely ethical and moral reasons....cough.... cough... there forms are often made of light which can be warm to intensely hot. They make our bodies tingle as their charged forms have out hair standup or play haywire with our synapses due to LMF they emit. They often communicate through CE4-1, CE4-2, CE4-3 scenarios with either lucid and telepathic mental constructs or manipulation in ones various energy fields. They profess they are about love and peace, but are very sensual.
Sex with these beings is all about fluctuating in our own bio-rythms and theirs, a mixing of wavelengths of mind, sound, and emotional intensities. We can have this type of sexual experience between humans, which we call "foreplay"...a lot of massaging and getting in the mood with music and altering our state of mind with some alcohol. Playing with them can be dangerous as they can get carried away, the energies may cause your synapses to go haywire and the radiation fluctuation can cause injury.
Reptilian/Draco
One of the last of the common aliens will discuss here in brief are the Reptilians or Dracons. These being usually appear as a near humanoid, but with heavy reptilian features. Most all have scaled skin ranging in various colors and textures. Some appear very serpentinal or lizard like, more often with snouts instead of our humanoid flat faces. Eye can be human like with different pupils, or snake like eyes of all black. Some have the double eyelid. Other have vary facial features sporting crowns, ridges, crests, and spines. Some have tails, and some have wings....either vestigial or functional. Lastly the musculature can very from dense and bulky to lithe and firm. The smell is reptilian some have said. So their physical form vary as well as their origin and temperament. Many claim they are from Orion and other say that earth is their home planet, and other claim that they were the Igigi that were given this planet by the Annunaki.
Sexual intercourse with them can be very rough or very sensual, but either way they are dominant. Male have a standard penis or hemipenis, similar to our reptiles, while the female have cloacas. As said they are very rough in the sense they know what they want....humans are just squishy plaything. Various people have lots of stories of love making with reptillians, many of which are surprisingly pleasant. Some even claim long distance relationship with their reptilian lovers. They definitely know to pleasure a human and are very sensual using their anatomy in every way to have an amazing tactile experience.
Cephalopod
This is an odd one cause it is something that is in the human zeitgeist and not necessary "alien" as it appears in supernatural phenomena and popularized in Japanese culture known as "Naughty Tentacles" in the hentai circles. This was the most General Audience friendly image I think I could use. Now it is not limited to just woman by the way, and their have been reports of octopus like aliens. Most are famously portrayed in media...such as "War of the Worlds", the "Simpsons", and "The Arrival".
The things is it is something that usually interacts with humans, not interested in sex... its more of exploration. The phenomena usually has the tentacles restraining as in bondage, exploring and stimulating the human orifices, exploring and stimulating our skin, entering our bodies and exploring them as far they can get, or implanting us with various fluids or eggs.
Again, this is mostly for a description of appendages which obvious have a phallic connotation to them. They appear in occult stories with summoning demons and other entities, intelligent sea creatures in crytozoology, and some abduction stories with machine or octopus-like aliens. Most of these encounters are not pleasurable, and at most consider non consensual.