Nothing different you just happened to be looking down at the time. The place is built in the middle of a swamp. There have been rats in that area for thousands of years. There is all kinds of food that thoughtful Guest throw about, and although Disney does its best to keep rats away from the general public, there is only so much anyone can do. I've been going there for 35 years with 45 trips and have yet to see even one.
I remember years ago when my wife and I were looking to buy a home, we looked in a place that had a meadow above the house where she wanted to be able to have her horse. As we were walking up to the meadow each step we took was accompanied by a dozen or so snakes that would scurry away in all directions. I swear if she had looked down even once she would have had to be removed by helicopter. I told her about it later and that place was immediately crossed off the list of possibilities.
