The top mistakes in Gacy http://www.moviemistakes.com/film5522 en Sat, 19 Jul 2008 05:55:26 +0000 101073 The movie takes place in Des Plaines, Illinois, with a couple of scenes from downtown Chicago. However, throughout the movie you can see both palm trees and mountains in the background, none of which actually exist in Illinois. The producers also point this out on the DVD commentary.