Those opening lines...

A colleague and girlfriend of mine who is ten or so years older and who has very different tastes than I do was out and about with me in New Orleans a couple of years ago.

We were hanging out at this one bar listening to the Blues and being served by this very attractive bartender. At some point in the evening, my friend approached the handsome barkeep and engaged him in coversation.

Girlfriend: "You are a very handsome young man."

Bartender: "Thank you, ma'am. Is there something I can help you with?"

Girlfriend: "Yes...Do you have an older sister?"

Bartender: {{Only momentarily dazed}} "You are lesbian, aren't you?"

Girlfriend: "Yep. So, are you going to introduce me to your sister?"