"You're too noisy, and your clothes too clashy. It's plain enough for some kids to fight, but you need to misbehave and squabble in a way that's far more disruptive."
The boy held up the socks, trying to process her words but giving up rather quickly. As impulse would have it, he screamed "It's her fault, not mine!" And threw it at his sister, inciting a scream from her lungs that died down very quickly.
The boy tugged on the oblivious parent to no effect, as her daughter tugged at her untidy bobbed hair, feeling a lot less combative than she did moments ago.