My favorite sim, or at least favorite game-play was with a sim whose name I forgot.
I created her in CAS, she started off at maximum body weight and minimum muscle. She became a scientist and had the aspiration to be a nerd brain. She lived in Oasis Springs and reached the top of the scientist career, meanwhile learning rocket science and becoming good friends with Johnny Zest and Bjorn Bjergsen, the latter of which she had a romantic interest in but he's a married man.
When she completed her aspiration of being a nerd brain and also finishing the computer whiz aspiration, I chose the body builder aspiration for her to lose the body weight and she turned out a super beautiful sim. Though Bjorn still wasn't interested so she thought of a plan to contact aliens and find an extraterrestrial husband. Alas, when she finally made contact and even went to visit the alien world, there were only female aliens! (Not sure why, it just was that way.)
So she invented a cloning machine and ended up cloning Bjorn. The clone turned out evil but she went with it and married him and had a child with him..
But then I ended up losing the save file when I had to re-install my game. Kinda sad that she's gone but I had some good fun. :D