Ignoring the lack of physics, bizarre clothing, gravity-defying hair, unusual writing, peculiar animation, and the like: What's with the fans?
The fans are nice people, they're fascinating, and they can be a lot of fun to be around, but they are rather bizarre. Case in point: Ask a fan of a series what character they hate the most in front of a group who like the same series. Then step back and watch the ensuing twenty-minute brawl as they all discuss the merits and follies of each-other's hated characters. They will buy and wear merchandise of their favorite shows to all occasions, do their hair in the same fashions, use the same phrases as the characters, and if given the chance they will even eat the same kinds of food as the characters. It's quite baffling to me how they attempt to disguise themselves as mere characters.
Now, I can see the joy in dressing up in new ways or pretending to be someone you're not (I am a steampunk geek now, and have snuck into the Cyberpunk genre before just for something new) but this goes beyond mere dressing up and playing pretend into the realm of psychotic copycatting similar in ways to that movie "The Roommate".
For example, look at the costumes. Some of the women's costumes defy gravity, animal-like creatures warrant mascot-like appearances, men and women playing opposing genders, men's costumes that require not only androgyny but absurd amounts of hair gel to make work. The costumes must have been difficult to make, especially since most of them do not look like they could feasibly stay on a person, much less function as clothes should (protecting skin and all of that)
Even more creepy are those who dress up for sexual reasons, but suffice it to say I will not go into that.
It's kind of creepy all around, to be honest. People spend large amounts of money building props, buying/styling wigs, making good costumes, buying manga, buying food, buying convention tickets, and all for... what, exactly? Maybe to show off, but there are far better ways to show off sewing talent. For example: Design some clothes that don't look terrible. The clothing market seems to need help with that lately.
It all just seems so pointless, But the important thing is: it's jolly good fun. These people are inviting themselves to have Halloween on more days than just one. Rather than trick-or-treating for candy, they hang out with friends, meet new people outside of the Internet, experience an unfamiliar culture while still being in their 'safe zone', and get to share in-jokes with people who will understand them. It's a socializing experience, and one we should encourage... so long as it stays within reason of course. To some of these people I would advise seeking mental help, but for the most part everyone seems to just be enjoying themselves and having a few laughs. There are bad cosplays and good cosplays, cute cosplays and creepy cosplays, reasonable cosplays and 'who-let-them-out-of-their-house-dressed-like-that' cosplays. So long as we can all laugh and have a good time, we should encourage it.
Now, where is my Dr. Who scarf? All this talk of cosplay has me wanting to join the fun!