The puppy playing Young Reggie was adopted by director Josh Greenbaum.
Real dogs are used in 95% of the film.
Josh Gad is the voice of Gus, the Labrador Retriever who was narrating his owners story at the fair. Josh Gad was the voice of Bailey in A Dog's Purpose and A Dog's Journey, in both movies, the dog narrates his owners story. And his owner in both movies is Dennis Quaid, who appears in this movie as himself who was bird watching.
The film uses a mix of real dogs with a few shots of an animatronic one.
This will be Will Ferrell's first time voice acting in a live action film as his four previous films Curious George (2006), Megamind (2010), and the Lego Movie films were animated films. This will also be his first time voice acting in an R rated (in the US) live action film as his four previous films with voice-over work were rated G and PG, as well as his first time appearing in a film with voice-over work to not feature either David Cross or Jonah Hill.