I've been looking for a list of hidden traits online and haven't found much about them. By hidden traits I mean traits that are NOT in CAS and are NOT in the list of traits that can be bought at the ...
The "is adoptable" trait came from a young adult who started out as a townie child and grew up in game. Maybe once they get that trait it stays with them for the rest of their sim lives.
@vanee4
Maybe it's like in Sims2 where they start out neutral and develop with game interactions. I don't know if it can be altered.