McDuff, the Talking Dog (1976)

Calvin Campbell is a veterinarian, who is also the parent to his sister Kimmy. Now Calvin though not very bright and confident is very nice. Now Amos Ferguson his neighbor wants to buy his property but Calvin refuses so Ferguson is always coming with a new scheme to get Calvin to sell and he almost succeeds. But fortunately for McDuff, a ghost dog who apparently has been watching Calvin's family for generations is there to thwart Ferguson. And McDuff is also a talking dog. But everybody thinks something's wrong with Calvin because they always walk in on him talking to himself cause McDuff only reveals himself to Calvin.