So, of course, in the great debate on whether or not it is cool to dress up and/or bring prop replicas to a movie premier I'm going to answer a resounding, "YES!"
First of all, this is a way for you to show that you're not just a casual fan who saw a cool trailer during last Sunday's football game. If you dress up in costume for a movie, it shows you're a superfan! You have knowledge and passion for the source material!
Second, it makes the entire movie experience more special for everyone. Why is it cool to go to midnight shows? Because, at its best, it is like going to a mini-convention for people who are fans of this one intellectual property. Anyone who was at a Star Wars or Harry Potter midnight showing knows what I'm talking about. It's cool to see how fans costume up to express their interest in a film and it's also nice to be stand out in a crowd yourself. Try walking up to the concession stand, sighing, dropping your Thor hammer on the counter and saying, "You won't BELIEVE the day I've had!"
Thirdly, it's a way to make yourself approachable to other fans. If you dress up you're saying, "I'm not just here to see a movie - I want a bigger experience!" This signals to other fans that they can approach you and begin talking. If nothing else they have an easy conversation starter ("Hey, nice costume!"). At Captain America alone I had a few fans approach me and ask where I got the cool shield (I pointed them toward Comic Store West). It's nice to gain a little attention from the crowd.
Finally, it's a way for you to express your own creativity. What's better than hobbling together a home-made Hank McCoy or Rouge outfit (I saw both of these at the X-Men: First Class midnight showing)? And, BONUS - Come Halloween or the next Con, you've already got your costume ready to roll. Score!
So as you clearly can see, shedding your inhibitions and dressing up for a movie premier is cool. It make the experience more memorable for you and everyone else. And after all, that's what most fans are after at a midnight showing - something more special than your average movie-going experience. So, God Bless you, Up Boy, and all the mega-fans like you!