Quote from Rose in Sister of the Bride
Doug: I think it's time you told her, Clayton. Blanche: Told me what? Clayton: I wanted you to meet Doug for a very important reason. Blanche: Well, why? Clayton: Blanche, we're getting married. Rose: Oh, that's impossible, Clayton. Brothers can't marry sisters. Oh, that's right, you're from the South. Dorothy: Blanche and Clayton aren't getting married, you airhead. Clayton and Doug are. Rose: Oh. Oh! Oh?