I would like to go to the San Diego comic con one day.  have you ever been?
I have once, for a short time only, its nice its a multi-genre entertainment and comic convention
I have seen on the internet that people dress up as their favorite characters.  Would i be out of place if i dressed up like Mr. Pickles, the dog from the cartoon network?
Nice, a lot of professionals, exhibitors, and pre-registered guests, you can get lucky and see someone famous too!
If i understand correctly, they just sit around and read comic books?  Between the costume, airfare, hotel, and meals, it seems like quite an expensive hobby.
Yes it is pretty expensive, and its a four-day event (Thursday–Sunday) held during the summer, so staying there also makes it more expensive