What kind of gameplay have you invented in TS4?

One thing I've done since back in the days of Sims 2 is to allow for "accidental" pregnancies. Before any couple does the woo-hoo, I roll a standard 6-sided die. If it comes up 6, I select "try for baby" even if this isn't in anyone's plans. It's led to some interesting storylines over the years. Unexpected babies have a way of complicating a lot of lives.