Nightmare Customers 101

I was thinking about the absolute exquisite service that employees of Walt Disney World display. I wouldn't know this form personal experience, but good friends and Marketing 101 textbooks can't be wrong. Then I started thinking about all of those worst-nightmare customers which exist everywhere known to man. Those Disney employees are trained, trained and then trained some more to always smile and meet the customer's* every need. I wonder how they deal with the nightmares?

* they aren't actually called customers, but I can't for the life of me recall what they are called