The showing I went to was hosted by a couple members of the Napoleon Dynamite fan club. They kept trying to spark Audience Participation moments. Doing the wave before the film started, throwing up Vote For Pedro signs, and various other things. I'm pretty sure that some of the other kids in the audience had been to previous screenings. During the dance scene bubbles started floating upwards from various areas of the audience.
I don't think Rocky Horror will have to worry about Napoleon Dynamite taking over the crown of Audience Participation.
I really need to catch up on my movie viewing. Still haven't seen Spider-Man 2, Farenheite 9-11, Arthur, Shrek 2, or actually a bunch of movies.