Never heard of "cosplay" before? Google it and you'll see it's hardly a minority/fringe interest, especially in the USA, Korea & Japan.
Everyone has a special interest and, if yours is particularly special, the web has made it easier to find those other few souls who share the same interest.
For the time being, the travel industry still focuses on 'mainstream' special interests like battlefield or garden tours, but slowly they are catching up (eg quilting holidays) and if there isn't an operator or travel agent specialising in your 'thing' yet, there soon will be... and this is the section where I'll list it!
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Photo: cc Flickr/Phoenix Comicon