The dog meets a few other people and pets who leave an impact on him during his many existences. Top Dog and Spike are two dogs who stand out as alpha males battling for control of the Yard. From them, Toby learns that sometimes a dog can't just bark—he also has to bite.
The humans of the Yard, Senora, Bobby, and Carlos, "have too many dogs and they will not give us a license" (1.13). They are keeping all their dogs in poor conditions, but Toby doesn't know any better, and he loves them anyway.
While a working dog on the force, Ellie has colleagues, Cammie and Gypsy, who are "working dogs and didn't feel free to play much because we always needed to be ready to serve our masters" (18.56). The dog has been serving various masters since his first life, so we're not sure how this is different, other than the no playing part. All work and no play makes Ellie a dull dog, we guess.
Finally, we have Jasper the Donkey, our pick for the number-three donkey in fiction, behind Eeyore and Dominick the Italian Christmas Donkey. A beloved fixture on the farm, Jasper lives for forty-four years, conveniently dying around the time the dog walks by the veterinarian's facility. Jasper's scent leads the dog to Ethan. He must have been one stinky donkey, but we still love him.