Fandoms
On some level, everyone who ever saw this movie is a fan, which lets us cast a pretty wide net. There are fans and then there are fans however… and you know when you spot a 400-lb. man wearing a version of Dorothy's dress that you've entered some next-level appreciation here.
The most well known organization for all things Oz Fan is the International Wizard of Oz Club, founded in 1957. They host conventions and events all over the world, stage readings of L. Frank Baum's original books, and have even published some of his hard-to-find manuscripts. That comes with a fistful of appreciation for the movie as well, and the group used to feature stars from the film at their conventions.
Speaking of conventions, Oz Con International, better known as Winkie Con, has spent the last fifty years hosting annual get-together for Oz-o-philes. They were rocking the cosplay long before those Comic-Con folks got into it, and they even host their events in San Diego like Comic Con does. Luckily, the folks down there don't bat an eyelash anymore at the sight of 40 people dressed up like the Tin Man.