Unmodded, it's a roll of the dice on alien abduction, with or w/o pregnancy occurring. You could have a long dryspell of no alien ship appearances, and then suddenly one night your sim is going into the clouds. MCCC opens up new opportunities that I am taking advantage of. What is fun is I started a new save with Island Living (I really need a blueprint save with my favorite custom venues already in place), and after one Aliens Night at the bar, I suddenly had aliens wandering around Sulani. Made me so happy. I love aliens and vampires, and the thought of both on a tropical island is just fun!