Walter the farting dog and the windy day - William Kotzwinkle

When Professor Kompressor attempts to cure Walter of his evil farting tendencies, the plan backfires. Instead of beign fart-free, Walter simply fills up with wind but he eventually floats high into the sky. He floats high above the world and knows the only way to come down is to fart but he's got severely trapped wind. Eventually he meets millions of butterflies who have been blown off course and are in danger of dying unless they can be blown back on course. Walter does come to the rescue, saving the butterflies and floating back to earth where he's picked up by a watchful park ranger. Everyone's delighted when he's reunited with his family - not least of all the deliverymen who've been suffering Walter's wind halfway across the country!