You May Now Kiss The...Uh...Guy Who Receives - S4-E25
Other mistake: When Peter is eating the Brownie, it stays the same with no bites.
Continuity mistake: When Stewie mentions to Brian about his "Life's a beach" mug, the squares on his calender keep changing size.
Continuity mistake: Peter falls from the roof of the Clam landing on Joan Cusack. He puts her body in a mailbox that appears just for this scene.
Answer: Mort is Jewish, and Walt Disney was said to be antisemitic. So it would make sense in a Disney universe all the inhabitants would share his supposed beliefs.
MasterOfAll