This may be the only time anyone ever says this, but thank God for Fisher Stevens. About halfway through “When the Party’s Over,” Stevens enters playing an artsy, groovy, perpetually positive Angeleno and rescues this 1993 movie. “Rescues” might be stretching it. He takes a snoozer full of unlikeable twentysomethings coping with their sudden realization of adulthood and turns it into a mere yawner. Sandra Bullock eventually falls for him, so we get to see more of her and less of Rae Dawn Chong and the rest of a forgettable, cliched ensemble spewing overwrought, pretentious lines. Get over yourselves already.