Instead of "Post Office," a couple gets turned on by a game of mortgage banker in a spot debuting today from Washington Mutual Mortgage. At first, the husband appears to be a mortgage official, then the viewer realizes he's at home, logged onto wamumortgage.com. The campaign created by McCann-Erickson Worldwide, Seattle, highlights expanded Web capabilities. Copywriter: Forrest Healy. Art director: Dave Moore.