You May Now Kiss The...Uh...Guy Who Receives - S4-E25
Continuity mistake: When Peter drives his car in the field it is perfectly visible, but in the next couple of shots the car's gone, and so are the tire tracks.
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.
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