 In order to bring some levity to the shoot,  William Peter Blatty (qv) suggested shooting a scene (not for the  movie, but to amuse everyone at the screening of the rushes) in  which Father Merrin would enter the house, take off his hat, and  reveal himself to be Groucho Marx (qv), a friend of Blattys. The  parody would even go as far as featuring an appearance from the duck  from "You Bet Your Life". Groucho was keen, but Friedkin got sick  that day and the idea was abandoned.