These are tweets by people (because Dogs can't use computers) pretending to be dogs, talking about their Owners (themselves) in the third person, and in some cases even changing the language level down a few notches to emulate a child (or what we would expect a dog to sound like.)
What really peaks my curiosity is the amount of work this is for the Owner (the person contributing) and what they seemingly get out of it. They could be anonymous if they choose to be, but instead they take on the persona of their dog, and away they go.
