Double Trouble (1967)
Jill is frightened by someone wearing a Chaney/Phantom mask at the Mardi Gras.
Three bumbling French-speaking Belgian detectives who are dressed and act like Closeau.
This is the movie that the two main characters try to see but which is sold out (identifiable from the poster outside the cinema)
Mentioned by Andrew O'Keefe as a possible answer to a question about the movie in which Elvis Presley plays characters Jodie Tatum and Josh Morgan asked when Xavier and the Chaser go head to head.