I have a lot of t-shirts, including many Disney ones, but never wear the Disney shirts(or sweatshirts) in the parks. Here's why. To me, the shirts are a reflection of my interests to everyone else. They tell everyone that I like scuba diving, Indy car racing, airplanes etc and have often became a conversation starter. But when in the parks, everyone already knows that I like Disney or else I would not be there. The exception for me is at sporting events where you are rooting for your favorite team. I guess you can make the argument that you can express your favorite character but that's still too close for me.