“It only takes six of my watermelons to make a dozen,” E.B. “Jelly Roll” Roberts used to brag, when he offered them for sale at his country store near the community of Cross-Corners, Texas. And he repeated the line over and over again, like it was the first time. Regular customers had long memorized the words and could mouth them as he spoke, but they always allowed Jelly Roll to finish. It was a respect-thing, like not stopping a friend when he's telling a joke you already heard. A true friend will even manage a convincing laugh at the end of the joke, and it's a real art form to make such laughs seem genuine.