A plot point for this episode is that Pat Mustard is on the phone to Ted, cackling evilly, for most of the third act. However, after Pat Mustard makes the initial call, Ted uses the phone to call two other priests for backup. Yet later on we see that Pat Mustard is still on the line, when Father Jack picks up the phone and listens in. So how could Ted make that other call when Pat Mustard was still on the line?
In the scene where Mrs. Doyle is telling Ted about the profanity in the book, several of the swears were not in the original script but were introduced by Pauline McLynn during filming. You can see Dermot Morgan trying not to laugh at her last line "Ride me sideways", which he hadn't been expecting.