Factual error: When Lois, Meg, and Chris go to the stage show on the West End, "theater" is spelled with the Americanism "-er" instead of the UK spelling "-re."
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.
Chosen answer: It's a real song called "Elvira". Originally by Dallas Fraizer in '66, however, this version seems to be the Oak Ridge Boys cover version. However, the mega lesbians skip the verse and just sing the chorus after the opening line.
Bishop73