Tips for making an Ultimate Sim?

That really IS a tough one. My favorite sim ever I think had a broken personality. She was just whacky and did some really odd things that I've never seen since. Like she'd go in the bathroom and just sit in the empty tub, or she'd cook a full dinner then autonomously stick the whole thing in the fridge without eating any. They were probably bugs, but she was a sim with the traits, "Creative, Genius and romantic" but she'd wear her formal clothing to go in the pool (Was NOT erratic) She was just goofy and broken and totally lovable. I miss her.

So, basically, I don't think I've ever had an "Ultimate" sim. Just a silly goofy one that stole my heart.