Continuity mistake: When Peter (from 1999) arrives at Quagmire's house for the stag party, the window is small. But in the next shot when Brian looks through the window, it is a lot bigger. (00:05:55)
Continuity mistake: In the scene with the multiple versions of Stewie and Brian come back to 1999, one Peter is with one of them. When Stewie asks everyone to vote between 9/11, Peter is standing in the foreground, but disappears when one of the Stewies says Brian had his throat slit. (00:18:25)
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