When we were on the Wonder last year, our family of 4 went into the theater to see Disney Dreams. There was a good number of people already in the theater, but we found some pretty good empty seats and headed toward them. We were already walking down the row from the left isle, when this mom and her son hurried in from the right isle and took the seats. She knew where we were heading and even made eye contact with us, but took the seats anyway. It's kind of like when you are coming up a row in a parking lot with your blinker on and heading toward an open parking space, and someone flies in from the other end and takes the space! She had her son sit on one end, left three empty chairs in the middle, then she took the other end. We were surprised, but backed up and found other seats a couple of rows back. Here is the best part, she kept standing up looking around for the rest of her party, and they never showed up! So there she sat, with all five of her chairs that she just HAD to save, with just her son through the entire show. We just sat back and laughed.
On another note to people who are cruising for the first time, we also met many friendly people from all over while on the trip. Please don't think everyone you come in contact with will be completely rude. I would say the "good" people far outweighed the "rude" ones!