The visitors to the studio are told they are about to visit the set of Horrors of the Black Museum (1959). That film, which was also produced and written by Herman Cohen, was actually shot in England, not at the U.S. studio.
When Rivero is reading about the third murder in the newspaper, he hands it to Dumond, who holds it so the back side and other pages are showing. The other pages are all blank, indicating that this paper is a dummy.