Other mistake: While Peter is questioning Carter how he could be having an affair, Peter's right sleeve suddenly becomes the same color as his skin for a few frames.
Continuity mistake: When Peter is eating dinner with Lois and her parents, on his plate there is mashed potatoes and meat loaf. Peter shovels potatoes in his mouth then spits them out all over the table. When his plate is shown again, the meat loaf has disappeared from the plate even though he didn't touch it.
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