Alien

An Alien is a life state in The Sims 2 for PC, Mac, console, and Nintendo DS. Aliens are not featured in The Sims 3, however it is possible to create an alien in Create a Sim. While alien abduction can occur in The Sims, aliens themselves do not appear, and creating them would require the use of custom skins.

Culture
From what little information is given from the family history of Pollination Technician 9, a player can see what appears to be a primitive, yet at the same time, complex culture on their home planet. At least to an outside observer, their society appears to be structured in a way not unlike that of bees, where individual aliens have roles parallel to the functions within a hive. Birth Queens are the central, and seemingly only, reproductive system of the aliens, except for the work of the Pollination Technicians. It appears that whomever impregnates them has no marital attachment to them, and that the sole purpose of a birth queen is to breed. Colony Drones are the workers of alien society. What work they do seems unclear, but it is assumed that they do menial tasks that would be equivalent to a working class Sim. Pollination Technicians perform the work of abducting and impregnating male Sims. They seem to be recent phenomenon in Alien society, as there are no known Pollination Technicians that have bred with Birth Queens.

Growing hair may be seen as a societal faux pas in the unseen hive, as they appear to be able to grow it, but don't unless they retire or emigrate off-world. Clothing is highly suggestive for Birth Queens, while being a uniform for males is in all avenues of profession. Children are presumably taken away from their parents, as evidenced by PT9's lack of parental relationships (he has no memories of his parents, grandparents, or anyone else in his family except his wife and children).

Careers
Pollination Technicians are apparently allowed to retire from their assigned jobs, and are then allowed to settle on planets. Pollination Technician 9 retired on his "favourite" planet, which is the one which Sims reside on. That he has a favourite obviously suggests that the Sim planet is not the only planet where the Aliens carry out their operations. According to PT9's careers panel, it appears that the Alien society has no outstanding pension plans for those wishing to retire abroad, as he receives none.

Young aliens, regardless of gender, seem to be able to seek higher education in Sim universities, which places the possibly sexist roles of Birth Queens as possibly being an optional career choice, as Stella Terrano is able to enroll in La Fiesta Tech with no difficulty.

The Sims (Console and PC)
Aliens only take an interest in those who take an interest in them. The Sim returns a few hours after his or her abduction with a changed personality. At this point in time, 25 years before The Sims 2, Aliens are clearly just beginning serious research on Simkind, and have minimal knowledge of Sims themselves - though the pollination of Nestor Caliente would likely have occurred prior to the events of The Sims. It is also too far back in time to tell what type of Alien carries out the abduction.

The Sims 2
In regards to Sims being abducted, Aliens take the dignified and fair approach of only taking an interest in those who take an interest in them. Only one type of Alien will carry the process out, the Pollination Technician, whose sole purpose is to abduct male Sims and impregnate them with their DNA. How this is done is unexplained. What is referred to by Sims as a painful, embarrassing and frightening abduction is merely "pollination" to Aliens, which inevitably results in an Alien-Sim hybrid.

Physiology
Aliens are capable of growing hair on their heads and face just like Sims, however, they are only capable of producing black pigment naturally, as they don't possess genes that would create any other colours. They have dominant green skin that is universally the same tone throughout the species, with no variation. They also have dominant black eyes, seemingly with either black iris and black sclera, or a single use of one over the other, or even neither, possibly with the entire eye being the receptor. Alien ears can vary in shape, being either very small or pointed at the top, suggesting semblances of races, like Sims. Faces are almost always long and gaunt, with either small Sim-like noses or pressed up slits in the center of the face. Mouths usually have thin lips, or none at all, and the inside of the mouth is light blue, the gums being the most prominent. Teeth are essentially the same externally. Alien bodies have the same metabolic rate as those of Sims. They age at the same rate as Sims, and gain or lose fitness when they exercise or overeat just as Sims do, with no advantage to either. Since the inner mouth is blue, it is safe to assume that the blood of Aliens is blue also, indicating that it is hemocyanin and not hemoglobin that is present in their bloodstreams, an indicator that they are not mammals. If so, it is very inconsistent, as lifeforms with hemocyanin cannot eat the same foods as those with hemoglobin, whereas those Aliens who have chosen to live among Sim kind eat the same food Sims do. As it is not known what Aliens eat on their own planet or ships, it is possible that those who choose to live off-world are first adapted to be able to eat the foods of their adopted planet.

Genetic Compatibility
Physically, Aliens, like Sims, are an accident of evolution. They are startlingly similar to Sims, to the point that they can reproduce with one another with no ill effects. Hybrids typically either have minimal differences or major differences from their Alien parent due to the nature of genetics.

Life State Compatibility
Alien physiology can adequately support Sim-earth based life states, with minor alternate differences mostly associated with the skin tone and eyes.

Origins
Aliens only have dominant genes, and universally detrimental personality traits such as shyness and sloppiness have been selected against, most aliens have "perfect" personalities, such as Pollination Technician, who can father hybrid children with partially perfect personalities; but some aliens have more varied personalities such as Pollination Technician 9 Smith. This "hyper-evolution" suggests that aliens have been sentient for a lot longer than Sims have, which is more obviously manifested in the far more advanced technology that allows space travel.

Aliens appear to be a hyper-evolved extreme of life, as their species has virtually no variation beyond facial structure and body structure. All pure aliens have the same shade of green skin and have genes for black hair and eyes. This suggests that all forms of genetic variation, such as recessive genes equivalent to light blue eyes and grey eyes in Sim DNA, have been selected against to the point where only the most dominant genes have come out on top -- in aliens, recessive genes do not exist. Whether this change is due to natural selection or due to the alien's social structure is undetermined.

Since recessive genes are almost never lost, they may be dormant in Alien DNA, potentially playing a part in future Sims games as a source of genetic variation to add to gameplay mechanics.

As Sims, like humans, are most likely also descended from dark skinned ancestors, it is possible that aliens had a dark green skintone early on in their evolution, assuming that they migrated from a hot climate like Sims and humans did and that Aliens are mammals. The skintone and eyes suggests that they may be descended from amphibious life or reptilian life. However, the presence of blue blood suggest that they have hemocyanin, which is usually present in Cephalopods, Gastropods and some Arthropods.

Physiology
Hybrid children can inherit normal looking noses roughly 2/3rds of the time, though the remainder can inherit the infamous slits in the middle of the face. 80% of the time, green skin is inherited (100% with first-generation alien hybrids, though they can have human-skinned children, assuming that their spouse isn't green), though there are some cases of children inheriting Sim skin tones, allowing them to blend into society unnoticed, assuming they did not inherit erratic facial features. Flamenco Caliente and Jill Smith are both prime examples of this. However, there are times when only partial resemblance is inherited. Those with Sim skins never inherit black eyes, though it is possible for green-skinned hybrids to inherit dominant Sim eyes instead of black eyes. Johnny Smith is an example of this. Typically, there is minimal ear difference. Long, gaunt faces are commonly inherited.

Since the alien parent usually has a perfect genetic personality (10 nice, 10 outgoing, 10 neat, 10 active), this is also partially inherited and passed on, which can last for generations before finally being diluted.

How to become impregnated by Aliens
There are five ways to become impregnated by Aliens in The Sims 2. Two ways are legitimate and three ways are via cheating, which poses a risk of the game being damaged if debugging tools are not used.

Normal gameplay

 * Telescope - A male adult Sim can stargaze with the Farstar e3 telescope until he gets abducted. The chances of this are at a modest 0.05%, which remains this way unless manipulated by mods or hitching a ride with the FreeTime aspiration point bonus. After the Sim is abducted, they will return a few hours later, pregnant with an alien hybrid.


 * Electro-Dance Sphere - If the player has the Nightlife expansion pack, male Sims can also be abducted using the machine if they have been abducted previously with either 2 telescopes, or if very lucky, the Dance Sphere. It is rumored that the the chances increase if a Sim uses the Dance Sphere with 10 Body points. This method varies in effectiveness between 1.65% to 2.5% depending on how many times the Sim has been abducted previously, but the chances are significantly higher than a telescope, regardless of how low it can get.

Cheating

 * In-game Debugging Mode - Entering the cheat  then shift-clicking on the telescope and choosing "Debug - get Abducted". After this point, the process continues as normal. Newer expansion packs have made this cheat impossible. All the Sim will do now is walk up to the telescope and cancel the action.


 * The Tombstone of L & D - Initiating the  cheat, then, shift-clicking on any Sim and spawning the Tombstone of L & D (Life and Death) allows the player to open up testing options to initiate quick pregnancy in any gender. The options "Make me alien pregnant" and "Speed up my pregnancy" in the pie menu make this the fastest, albeit riskiest method of all. Both options will work, regardless of gender.


 * Create-A-Sim Debugging Mode - Enabling the  cheat allows the player to hold Shift+N to unlock alien skintone and eyes, along with hundreds of other features hidden by the game in CAS. It is turned off by holding Shift+M. This method of cheating is the safest, as there is minimal opportunity for the game to crash as it likely would in normal gameplay. Furthermore, CAS only creates Sims without any varied recessive traits or extreme personalities that would be inherited with normal hybrids such as 0% chance getting abducted when stargazing as an alien-sim hybrid, although these values can be edited by those knowledgeable enough to change these values in programs such as SimPE.

The Sims 2 console versions
The player can create aliens by randomizing appearance in The Sims 2 for console. All aliens have at least 1 alien in their family tree.

The Sims 3
Aliens are not featured in The Sims 3 base game (or any expansion pack to date) however it is completely possible to create them, without subtle details like the blue gums and full-black eyes. Additionally, subtle differences in green skin tone can be made, which wasn't present in The Sims 2. But they must be flying tigers to fight them