Revealing mistake: In the scene were Mrs Doyle is listing the rude words and phrases used in one of Father Ted's favorite author's book's, she goes through all of them fine. Apart from the last one, when she says "Get your boll*cks out of my face" you can hear her laughing in the word "boll*cks" before she exits the room.
Audio problem: When Bishop Brennan calls for the first time at the start of the episode, Ted panics and pretends to be French before hanging up the phone. You can still hear Bishop Brennan talking on the other end of the line for a few moments after Ted hangs up, which obviously shouldn't be possible.
Revealing mistake: At the end when Ted flushes the toilet and kills the priest, we see an outside view of the priest and if you look at the bottom of his robes you can see a black square thing hanging down from the inside which must have been squirting the water out of his robes. Also to prove this, you are not able to see any water coming from the drain in the ground, which does not make any sense.
Continuity mistake: In the scene where the old women are grabbing at Eoin at the front door in one shot the top pane of the window on the left of the door is broken and an arm is coming through it, in another shot the bottom pane is broken and the top one is intact and arm is coming through the bottom pane and in the very next shot the top pane is broken again and the bottom one is intact again. (00:13:05)
Continuity mistake: As Father Crilly is shouting at Father Jack "No, not your room, not your room." to get up out of the spare bed, watch closely and as Father Ted strikes him in the face, notice that his hand doesn't even touch his face, and his hand stops several inches away from his face, using only his reaction and the sound of a punch to illustrate a punch at all. (00:18:15)