Continuity mistake: When Stewie has chicken pox the red marks on his face change position many times between shots. A noticeable one is just as he is saying "No, damn you, I've got to finish what I started".
Continuity mistake: When Stewie and Bertram are parachuting down to Earth after the air strike, their parachutes get much closer to each other between shots. This occurs just before they start slapping each other.
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