I work at McDonalds, but I rarely work in service, that is, with the customers. I normally cook the meat or assemble the sandwiches, so I've never had to personally deal with the woman we call curler-lady(She always comes in with curlers in her hair). She will always ask for things in a very specific, confusing, weird way, such as a McDouble with every condiment on the side, as well as shredded lettuce, but, that alone is fine, it happens sometimes. What isn't alright is that she's incredibly impatient with people who don't immediately understand what she wants, and she is also incredibly racist, once saying "There is this n-word that used to work here that I don't see anymore. I guess the n-word got fired."

Other than that, just generally rude customers are pretty common.