Just this week I was having a conversation about how a size differential between two dogs became a problem for an owner. In this case it was a Chihuahua versus a young collie puppy. In “The Secret Life of Pets,” it is a small terrier mix left alone with a large brown shaggy dog. Everything about the beginning set up for the otherwise amusing animation feature was wrong.

1. When you get a new dog, particularly an adult, you should bring the dog to meet the new dog before deciding to adopt. The better rescues and humane societies will allows and even insist upon this.  Like people, dogs have preferences and sometimes will instantly like or dislike another dog. In the movie, Katie brings home the new dog, Duke, as a surprise to Max.
2. The dogs should meet in a neutral place. Dogs can be territorial in their homes. Katie introduces the dogs in the apartment which has been Max’s territory.  Bringing a new dog home, one suggestion is to have them meet in a neutral place and then walked home together.
3. The dogs initial interactions should be monitored and controlled. Sleep arrangements should be safe for both dogs. Katie let Max sleep on her bed, but when she brings home Duke, she closes her bedroom door and leaves the two dogs alone in the living room area.  Duke uses his size to push Max out of his bed and then takes the blanket meant for him.
4. A new dog, particularly one from an animal shelter, might not be housebroken. You can save yourself some trouble by limiting your new dog to a specific area in the house and crating it. Katie brings Duke in and then assumes he will be okay with her routine. If both dogs have their own crates, then there will be no problem with fighting over sleeping places. Crate training also makes it easier to house train a dog and ease him into a regular schedule for bathroom breaks. Dogs who are crate trained can be taken to hotels and will be less stressed at an overnight vet stay where they may not be kenneled but put in a small enclosed area.
5. Dogs can be aggressive toward food. You shouldn’t approach a dog that is eating something. Two dogs might fight over good. Katie feeds both dogs together and leaves them. Duke eats all of the food. This could have been avoided if Katie monitored their eating or fed them both in crates. Initially, two dogs should be fed far apart.
6. Duke is not introduced to the dog walker. The dog walker would be a stranger.
7. Duke isn’t introduced to other dogs of the dog walker. The dog walker would also have to introduce the new dog, Duke, to all the other dogs.
8. Dog walkers should not be taking dogs to the off-leash dog park. Many dog parks frown upon it. Most people cannot keep track of more than three dogs.
9. Generally, at dog parks there is a separate area for small dogs and large dogs. Large dogs can unintentionally hurt smaller dogs and a large aggressive dog can kill a small dog in an instant.
10. If your dog or cat can get out of your apartment, then it is likely that people and other animals can get in. One of my first roommates in Los Angeles let her cat roam. It killed a bird in another apartment. Her solution was to dump the cat at UCLA. She picked the cat up after a day and decided, she’d dump the troublesome cat in the country. I moved out before that.

Small dogs and large dogs can get along, but not all dogs get along. While I liked the movie, “The Secret Life of Pets,” much of the best parts you’ve already seen in the trailers.

The young collie I have is exuberant, energetic and aggressive. She does well with my two larger collies. I would worry about her with a smaller dog. I would worry about a smaller dog with my two larger dogs who have knocked over people and large, heavy pots while playing.

I hope “The Secret Life of Pets” will come back and develop the characters it introduced, perhaps for the smaller, more intimate format of television.