There is absolutely no doubt that DreamWorks has a hit on their hands with Dog Man. The movie based on the graphic novels by Dav Pilkey is a hit with children and adults alike. There is a way for DreamWorks to build on the franchise, and it's already introduced the character.
Caution: There are some minor spoilers from the Dog Man movie when it comes to Big Jim's introduction.
Big Jim is a cat who is only seen now and then in Cat Jail. He unintentionally helps Petey the Cat escape Cat Jail most of the time, and he comes across as a rather dimwitted character. Every animated movie has that one character who shows up now and then for side-comedic relief, and Big Jim is that character in Dog Man.
He is the way the franchise can grow, though. Like with the Penguins in Madagascar and the Minions in Despicable Me, there's a bigger story to tell. In fact, Pilkey has even told some of the story.
Big Jim is a superhero in Dog Man
Despite being in Cat Jail, Big Jim is actually a good guy. He is known as Commander Cupcake in the graphic novels, and there's a huge backstory shared in Dog Man: Big Jim Begins. It turns out that while he's in Cat Jail during the day, he is a superhero at night, opening up a story to tell.
Without giving away a lot of spoilers from the graphic novels, Big Jim does have a fairly heartbreaking backstory. He's an orphan, and this full story hasn't been told yet, but there is an opportunity to delve more into it. Then there's the hypnotist storyline that leads to him being addicted to cupcakes, which is certainly something for the franchise to delve into.
At his heart, Big Jim is an optimist, although it does make him a little dim-witted at times, especially when it comes to trusting that others are telling the truth and being nice. Some of the scenes from the graphic novels have already been shown in the first Dog Man movie, but there's plenty to explore with Big Jim, including how he ended up in Cat Jail.
So, if DreamWorks wants to continue expanding this franchise — after all, Dog Man is a sequel to Captain Underpants — then Big Jim is the way to do it. I think a lot of Dog Man graphic novel fans will agree.