Continuity mistake: When Brian stops at the Marriott, he orders a Jack on the rocks. As he is ordering it, there is a woman in the background with a martini, then when the camera cuts to behind the counter when Brian receives the Jack on the rocks, the same woman has red wine instead of a martini.
Other mistake: Joe salutes Quagmire's Dad. His legs are paralyzed, yet he uses them to push himself backward in his wheelchair.
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