The Littlest Hobo (1979)

London is an extremely intelligent, wandering German shepherd who walks into a different place in each episode of this long-running television series, and comes upon people down on their luck or in trouble. London always befriends and helps the struggling person or persons. Then, when his job is done at episode's end, London declines to be the pet of the people he has helped and departs to continue his cross-country drifting.