When the lead character in a movie has a pet; we feel immediately drawn to them as we perceive them as animal lovers, so they can not be all bad. Some film makers spend weeks deliberating which animal to use in their movie. But the success of "Lemony Snicket's Unfortunate Series of Events" shows that a mismatch of dogs, cats, snakes and fish also works well.
Both life action and cartoons have been built around a central character / s that is an animal. Here are some of my favorites. 101 Dalmatians has been both a Disney cartoon and a life action movie. The main human is the wicked Cruella Deville who wants Dalmatian puppies to turn their coats in her coats. It's a great romp with Cruella getting her comeuppance in the end.
One of my favorite childhood movies was the fantastic Disney animation 101 Dalmatians. I cheered as Pongo and Perdita rescued not only their own pups form Cruella Deville, but many others along the way too. Dr Doolittle was a famous movie starring Rex Harrison, and a trilogy of films were made in recent years starring Eddie Murphy as the guy who could talk to animals, but did not want to!
Having an animal as a partner or companion is quite normal in the world of movies, even to the point of them also being a hero. One such example is Milo, the dog who accompanied Jim Carrey through all his adventures as The Mask. Way back in 1939, everyone wanted a little dog just like Toto. He never left Dorothy's side as she went through her great adventures in Oz, and was there when she returned to Kansas.
Computer generated imagery has made animals seem lifelike and has added to the fun. What make it better is that the movie superstars are queuing up to give these cartoon wonders a voice.