There is something about Iz's crying that makes Leelo lose it.
This didn't used to be such a big issue, as Iz used to be a stoic. Lately, however, she's been prone to big sobbing fits whenever disappointment strikes. Which, maybe because she's five, is often.
Here's what should happen, ideally. Iz starts crying. I take her out of Leelo's earshot, and remind her, as calmly and gently as I can, that not getting to watch Tiny Planets when her daily video quota has already been met does not merit this kind of reaction. No one has died and she has no visible wounds. If she insists on wailing anyhow, I tell her I'll be in the other room and she can come get me when she's done.
Here's what usually happens, instead. Iz starts crying. Leelo notices and starts wailing, getting increasingly upset. Something tells him that if he start smacking his sister, she might stop and then he won't have to be so agitated. If I don't invervene before this happens, Iz gets walloped and her crying becomes epic. Leelo then becomes furious and hysterical. I consider dual stasis chambers for my children, and try very hard not to start weeping myself.
Eventually, and if I can keep them apart long enough, I can convince Iz that if she takes a big breath, smiles, and tells Leelo that she's okay, he'll stop being so upset. Thankfully she's now old enough to grok this concept, and it usually works. The children resume non-injurious playing. I reach for the bottle of Maker's Mark.
Leelo doesn't do this around any other crying child. I guess that's a good thing.