It's a Dog's Life, I Guess...

A little girl walks down the street one day looking for her lost chihuahua. She sees Ralph and mistakes him for her lost dog. He goes along with the gag, trying not to hurt the poor kid's feelings. After seeing that her family is rich and owns a big house, Ralphie makes himself at home. However, he learns about the drawbacks of being a dog (like a trip to the vet) and after a while, runs away himself. After escaping, he manages to find the real lost dog and reunites it with it's master.