Okay, so this isn't like the "make a ugly sim in CAS and then turn it pretty in CAS" yeah no. It's a long challenge, and I'm starting right as I'm writing this. It's basically just you make a ugly sim (read CAS) and you go down generations to get a pretty character.

And when I mean ugly, I mean ALIEN ugly.

~ CAS ~

Create the ugly sim. Non-natural skin tone, hair color, eye color, eye shape, fat (not saying that being fat is ugly), and so on. You HAVE to randomize the clothes and name.
For the traits, they really can be whatever you want... But you might want to choose traits like "flirty" or others similar so the game will be a little easier.
Oh, and they can be whatever gender.

~ Gameplay ~

The goal of the game is to go through enough generations that you have the most beautiful sim in the game. Like those sims that Youtuber simmers make of Sims4 with the CC. You know?
Your first character CANNOT learn skills or work. She/he must spend all her time flirting with men, marry one, and have one child with. Raise that child until they are old enough to move out, then leave.
The new sim has to flirt with men/women and marry one, have kids, blah blah.
Repeat until you have the most beautiful sim ever and you win!

~ Extra ~
You can't use cheats.
After the first character you can customize the outfits as you please, just not the face or traits.
All generations after the sim you created can work and learn skills.