I went to a midnight screening of The Dark Knight last night because I am a dork. I arrived at the theater a little before 10 PM, and there was already an intense line outside the theater. Many people were in costume (including several fans in "Elect Harvey Dent" garb), but the dude who took the cake was wearing an exact recreation of the Joker's make-up in the movie. I ended up sitting right next to this guy in the theater, and initially I thought it was charming (I dressed up for a movie once, though it's too embarrassing to reveal here). However, as the movie unfolded, the make-up dude became more and more disturbing. This is a testament to Heath Ledger's performance, as he frightened and disturbed me so much that I completely forgot about the fact that it was Ledger's last role. Something horrible would happen on screen, and I was constantly looking to my left to make sure the guy in the make-up wasn't trying to recreate it.
So, to the dude in the Joker make-up sitting next to me last night: if your goal was to freak out the squares (like me), then mission accomplished.