THE PUG DOESN'T HAVE the precision of a Border collie, or the speed of a Shetland sheepdog, or the perfect obedience of a golden retriever, or the nose of a blood-hound, or the power of a Doberman pinscher, or indeed very many qualities at all that would mark him as a canine athlete. What he does have going for him is a sense of humor, a love of showing off, the heart of a mastiff, and an abundance of charisma.