Continuity mistake: The buttons on Chris' and Peter's suits switch sides while they're at church. Also, when Lois goes to see Joyce after the news anchor's exposé, both women's buttons are a problem when the buttons do not change sides in the mirror's reflection. (00:04:00 - 00:13:30)
Continuity mistake: After Joyce reveals the secret on the news it soon cuts to Joyce sitting in front of the mirror at Quahog 5, and in the mirror's reflection we see the door behind Joyce opens at the real Lois' right side (blocking the lightswitch), but in the next shot facing Lois the door opens the opposite way (not blocking the lightswitch). (00:13:25)
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