Ok.
However, alien life state isn't from the base game. They are from Get to Work. I even googled it to see if I missed something. Nope, no news of them being brought to base game like Photography skill was. The base game does feature a green skin tone to all sims and little alien critter collection for sims using the space ship, but for alien life state, alien-specific eyes, alien abduction etc you need Get to Work. You could try removing Get to Work expansion pack and seeing if you can add an alien in CAS.
That is why I'm against it being a pack: it would be alien version of My First Pet stuff, aka DLC for DLC. I'm rather for it being done as Get to Work refresh.