Arnold Schwarzenegger had a few conditions before accepting the role of John Kimble; he wanted Ivan Reitman to direct the film, he wanted a physical fitness theme, and he and Reitman wanted broken homes, child abuse and family life written into the script.
Owning a pet ferret, like Kimble does, is illegal in California - a ban which former governor Arnold Schwarzenegger supported, fortunately this film is set (and filmed partially) in Astoria Oregon where it is perfectly legal.
Arnold Schwarzenegger worked with Pamela Reed again in the movie Junior (1994) which was also directed by Ivan Reitman . Reed portrayed a pregnant woman with a big appetite, quite similar to her character in this movie. He also worked with Danny DeVito in Junior (1994), a candidate for the role of John Kimble, but was not given the part due to his height.
Arnold Schwarzenegger speculates that the film could have grossed an extra $25 million if it were less violent. But Ivan Reitman felt like the violence "had to be there or the film would just peter out at the end."
When Kimble carries Phoebe into the motel, he says two short sentences in German (the only time Arnie can be heard speaking his native tongue in a movie.). For interest, these mean: "That makes me stinking mad. Now I'm mad."
On April Fool's Day 2012, as a prank, it was announced that the film was selected for a release on DVD and Blu-ray Disc as part of the Criterion Collection, a video-distribution company dedicated to the release of "important classic and contemporary films". It was said to be selected as important in part because of its genre-revisionist use of both the policier and family comedy genres in the same film.
Arnold mentions to his partner that he comes from a family of police officers. In real life, Arnold's father was the chief of police in his hometown. Arnold himself wasn't a police officer; he did, however, serve for a year in the Austrian Army.
The trivia item below may give away important plot points.
Throughout the entire movie Kimball continues to assure people that the ferret doesn't bite. Ironically, at the climax of the movie, Dominic is saved when the ferret crawls out of his jacket and bites Crisp in the neck.