I posted this in another thread "little things" but it fits here also!
When kids are playful they will taste the contents of the fountain that came with the luxury pack. (they use their fingers and get very playful)
Mischievous Sims can add stuff to the fountain that can make other Sims who drink it act "drunk". If Sims eat strawberries from a "tainted" chocolate fountain it may make some Sims sick or dazed.
Playful kids will autonomously dance with a manikin without music.
Mean, hot headed kids can make siblings sad and a parent can then comfort the child. Parents may get an angry moodlet about the smashed doll house. (they have to see the child smash it)
Parents have the interaction that deals with a child's bad behavior. I forget exactly what it is. It's not always available.