It's prom season for international celebrities, or as they like to call it the Cannes International Film Festival. The weeklong cinematic fete makes the Oscar red carpet look like a backyard barbecue. This week, in Southern France, you can wear a ball gown with a 6-foot trail and still be underdressed. To deal with this predicament, stars (and wannabe stars) go to extremes to compensate. It isn't always pretty.