Keep water squirt bottles handy, one in every room if need be, to help break them apart. Hollering may or may not work, it sure gets you more worked up though. And I am sure you know not to try and separate them with your hands; that route leads to the ER!

As to WHY, who knows? Until we have better translation apps from English to cat-speak, I sure don't know what gets in to them. Geesh! Hope you have a calm night!