HBOThe final season of Curb Your Enthusiasm has been fairly low-key as far as big, flashy surprises—not that Larry David seems like the kind of guy to make a to-do out of anything. But the penultimate episode, which aired Sunday on HBO, featured a cameo that stands as one of the biggest in the show’s history. Bruce Springsteen appeared as himself in a storyline about—what else?—how crappy Larry is to everyone around him, including the Boss. And while his presence may be enough cause for celebrat