What is your favorite feature, even tiny one, in the franchise? (Not just the "main" games!)

I really, really love the way babies act in Sims Freeplay. When I moved over to playing Sims 4, it was sooo disappointing at the needy furniture they had become. I don't even tend to play families that much!
I also really love, as a tiny detail, that sims in Discover University gain charisma skill when they're giving a presentation. When I first saw that it made me smile. It's the smallest thing, but I just love it.