In normal gameplay: it seems Sims are more likely to be abducted from a high point. Place your expensive telescope on the highest point of the lot, on a tower or the roof maybe. Only the expensive telescope allows abductions.... and of course only MALE Sims can get alien-pregnant in normal gameplay.
Not ALL babies born by abduction are green. Some will have the skintone of their "mother". But they may well inherit the alien eyes, hair (or lack of) or other features.
With boolprop testingcheatsenabled true
shift+click on the telescope.
From the menu choose Debug - Get Abducted
Type boolProp testingCheatsEnabled true
Press and hold the Shift key while Left mouse clicking on the victim - err- Sim
Click on spawn
Click on Tombstone of L and D
The Tombstone will appear near the Sim.
Left click on the tombstone and you will get lots of options: one is Alien pregnancy. This works for both male and female Sims.
Once the Sim's pregnant state is set the pregnancy will continue even if you turn off the cheat (by typing boolProp testingCheatsEnabled false). You can delete the tombstone.
I used this to make a family with five children, three of which were completely green-skinned, two brown with alien eyes. But both mother and father gave birth and they needed three nannies at a time :)
You can make a nicer looking alien pollinator in Create-A-Sim. He won't be able to abduct your Sims, in the normal way of things, but he can "pollinate" them by means of the normal Woohoo - Try for Baby.
There is a cheat for this.
In neighbourhood view Open the cheat box
Type boolprop testingcheatsenabled true in the cheat
box.
Go into Create A Sim screen.
Hold down Shift and press N
CAS will go into Debug mode and give you a
warning.
When it is in Debug mode, all the Maxis skins, work clothes, etc. are unlocked.
Choose the green alien skin,
and the full black alien eyes, if you like.
To turn Debug mode off by hold down Shift M
Go back into your cheat window type boolprop testingcheatsenabled false to
turn off the cheat.
Your Sim goes through looping animations while using the "stargaze" option
with the telescope. Each time through the loop takes about six Sim minutes,
the duration of one of the telescope animations. Once each time through the
loop you have a slim chance of getting abducted if the Sim is eligible (teen,
adult or elder, not young adults or children) and the time is between 7pm and
4am.
The odds of getting abducted during each loop are 5:10000, or 0.0005%. That
seems really remote, but since you go through the loop many times, it
eventually adds up. If you observe for an hour, the odds of abduction are
about 0.5%. If you observe all night (9 hours), the odds are about 4.4%. If
you observe all night for a week straight, the odds are 27% for getting
abducted sometime during that week.
Thanks to Tom Schumm for this information
The code for the telescopes appears to have been changed in Apartment Life.