I don't even consider most things I enjoy fun......my emotions especially the positive ones are rather lacking, so I don't usually get to the point where I actually consider something fun there are things I prefer though. There are very few things I would actually describe as fun, its rare for anything to cause me so much excitement I find it fun.
So yeah a lot of times people take it wrong and get mad at me for not enjoying myself, and I am sure if I told them I don't know how they would think I was being a smart ass....chances are if I am not talking about something that upset/angered me and seem calm I am enjoying myself as much as I can..but they expect smiles, giggling, and more facial expressions or whatever I guess.