I can't specifically address the 5 night cruises, but on ALL the cruises "formal" has become increasingly less formal thru the years. It is now more like "dress up if you feel like it" night. On the Wonder, it is called "dress up optional," and relatively few people go beyond "church clothes." On the Magic, it is still called formal and semi-formal night, but the dress ranges from jeans to tux and nothing is out of place. Check out this thread for more info.
Characters are much more accesible on the cruise ship then the parks, and you never know where you will run into them.
One of my favorites is my girls love the port hole windows on deck 4, and they spent hours sitting there, my oldest was reading a book and Mickey Mouse was walking down and stopped and put his hand on her book and the look on her face was priceless, but of course I was not fast enough with the camera.
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