Bruce Cameron On ‘A Dog’s Purpose,’ Josh Gad, Screenwriting [Video Exclusive]

I was dating this woman, her name was Katherine, still is Katherine, and she had adopted a dog, as an adult, she had never had a dog growing up, and the dog died rather unexpectedly, and she was completely unprepared for how gut-wrenching the grief is, when you lose your best friend. So we were driving up the coast of California, and she said she would never ever have another dog. And this was not good news for me, because I was starting to feature Katherine as being an important person in my life, but I want dogs, I've always had dogs, and I've always loved dogs. So I wanted to come up with a way to try to communicate to her that what her dog really would've have wanted most was for her to have another dog. And I make up stories as a way to make points and I started telling her a story about this dog who reincarnates and remembers each life and eventually learns so much along the life's journey that he figures out he's got a purpose and whatever that purpose is must be fulfilled in order for this reincarnation to cease. I told her this story, she did feel better, she did agree that we could adopt a dog. She liked the story so much that she married me. But she said you gotta write that as a book, that's a book! And I hadn't really considered that, but we were on writer's strike, and we're not allowed to write screenplays or anything else when you're on a writer's strike, but you can write books. So I sat down, when I wasn't carrying a sign in the driveway, saying whatever it said, "unfair," "boo," "mean," whatever the sign said. When I wasn't doing that, I was writing this book, a dog's purpose. Coincidentally finished it right about the time the writer's strike ended, which I don't know how that worked out. But anyway, that's the origin of the story for "A Dog's Purpose."

Oh yeah, it was a tiny book, a small release, small printing, not a ton of money for the advance, and it opened on the NYT's best seller list. We didn't see that coming. The publisher was certainly surprised. So I was very pleasantly surprised by the success of the book.

It's mostly a process of throwing out things you really love. It really is as if a girlfriend gets mad at you and throws all the clothes out into the bushes. You're throwing stuff out because no one's gonna sit through a nine hour movie, which is how long it would take to shoot every scene from the book. So it's very painful. It really is painful to say, but I love that scene, and then realize well, sure, it's a great scene, people read a Dog's Purpose, but there's a lot in there that's not in the movie for them, because it's all a process of tossing out.

He makes the movie. He so delivers on the premise of a Dog's Purpose, which is, dogs are so joyful, they're so happy, they're so optimistic. Josh, again, just absolutely nails that. But he was fun to watch the movie with because he laughed, and he sobbed, he really expressed his emotions throughout the movie. I feel like I found myself tearing up at scenes because he was crying.

I don't wanna give away too much, but I will say nearly everything with the dogs in it. There's a scene with the dog, it's an aerial shot, the dog is running through real tall grasses, and the dog just has this boundless joy, as it's leaping through the grasses. There's something so beautiful about that -- a dog off leash just having the time of his life. That, oddly, I teared up at that, and it was very moving to me to see how much joy was at the heart of a dog. This was a working dog -- it was supposed to run across this field, but it didn't know it was happy. It thought, "I get to run across this field! Nothing could be better than this." But the scenes toward the end of the movie, with Dennis Quaid. I gotta say, his interactions with the dog, he's such a great actor and he brought so much of telling the life story of this man, in just a few scenes and a few facial expressions, it's a very moving performance, very subtly done. He really delivers.