One of the BEST things I'd ever seen was on line for RnR. A family got on line behind us in the FP line. It was mom dad little girl of maybe 10/11? And her little bro. The girl was having an absolute tantrum over the idea that she thought they were in the wrong line. They had FP like us, but the girl kept insisting they were in the wrong line and wanted them to go over to where you GET FP (back when there were paper tix). Dad tried to explain that was the line for people getting FP and our line which was stretched out past the entry point a bit was the correct one. I guess the kid was livid at the idea of the FP line appearing long and insisted it couldn't possibly be the right line.
So she began carrying on and stomping her foot and being very very ugly and rude to her very calm family. After a few minutes of her tirade, her Dad took her by the elbow and guided her away from the line about 20/30 feet. He bent down, very close to her face and while I couldn't hear every word, I could make out the words "Will leave right now." very clearly. He never raised his voice, but was very firm. And when the princess rejoined her family she apologized very heartfelt for her behavior "Sorry, everyone. So sorry." And they went about enjoying the ride quite pleasantly.