OP tell me if you mind... but I'm ending up posting favorites not just one favorite. I do really love my Sims.
Today I played for awhile in a save where I have Sims 1 and 2 characters. I made Mama and Elden Hi.cks from the first Sims Game about a month back. Mama has become a favorite because I've really enjoyed her backstory. She lives with her son Elden who is a teen in my game and their three dogs - Bobo, Duke and Leroy in a run down trailer. Mama (per Sims lore) was rich at one point and a beauty queen - Miss SimCity... she lost her money to a psychic phone friend. I can see it happening where she got money fast and lost it fast.

I play her as an aging beauty queen who still kinda has it but knows it's going real soon. She's flashy, kinda trashy and really reminds me of Flo the waitress in a sitcom I'm pretty sure most of you won't have a clue existed called Alice. Mama's big dream is to marry a rich man that will support her and her son in a way she thinks she deserves.
I loved dressing her almost 50's style.. and she's a hoot flirting it up with anyone she thinks has money. She does go on quite a few dates.
The family overall is a huge challenge for me to play. I'm not use to playing so many sims at once so I rotate back to them now and again but can't play them day in and day out. If I'm on another male sim in that save game the sim I'm playing might take Mama out on a date. She's also always out and about in town and I can't help but make every other sim I play in that save meet her... and usually friend her. I've grown to really like her even though I didn't make her in a way that I thought she would be very like-able if that makes sense. I love it when my game throws me for a loop.
edit for a dog name... no clue why it's plummed out bo.bo is the dogs name. If that's some kind of curse I don't know about umm sorry or let me know.