I used to hear this played in a pub near DC. The guys and the girls used to cat call each other each verse, right after "said to her." It'd be something like

[...said to her:]
guys: Hey wife you bitch
girls: Whaddya want you f*ing bastard
guys: Head
girls: In your dreams
guys: On your knees
girls: It won't reach
guys: That's not what your sister said
girls: That wasn't my sister, that was your brother
guys: What's the difference?
girls: Six inches

Has anyone else heard a similar sort of audience participation? If so, please correct/complete my rendering of the lyrics.