The number the Mayor gives to Chief is a real phone number. It even repeats the same words as in the film.
The first act of the film parallels the plot of RoboCop (1987), in which a slain police officer is reincarnated as a 'super cop'. As he grapples with the memories of his past life, he visits his old home and questions his identity.
Isla Fisher was already quite familiar with the source material before signing on to voice Sarah Hatoff, as her children are fans of the book series.
Like the book series, this is a spin-off of Captain Underpants. Dog Man is the fictional comic book created by George Beard and Harold Hutchins.
Although never stated in the movie, Grandpa's full name (unlike the books where it is Crud) is 'Garfield F. Heathcliff' in a nod to the three most famous animated cats. The F standing for Felix.