My good friend Evan passed this one along:
A Southern lady and a Northern lady found themselves sitting together in first class. The Southern lady, always mindful of her manners, turned to the Northern lady and asked politely, "So, where are y'all from?"
The Northern lady looked down her nose at the Southern lady and responded icily, "I'm from a place where we are all educated enough to know to not end a sentence with a preposition."
The Southern lady pondered this for a moment, then nodded and asked, "So, where are y'all from, bitch?"