The film's script was written over the course of a month and the idea generation involved deep discussions of each of the filmmakers' childhoods.
Principal photography for the film was shot in a week and made to look like fall when in actuality it was heavy winter. Snow can be seen on rooftops and in trees.
In early drafts of the script, the writers played with the idea that the character of Ira could traverse through walls from Joy's perspective. This is hinted in the final cut of the film when Ira seems to disappear in the kitchen scene. The idea was that she had so many extra curricular activities that, to Joy, she was superhuman.
The Creature that Russell fights in the backyard can be seen in the newspaper Ira is reading in the opening kitchen scene. He is the lawyer suing Russell's company.
"The Adventure's of Dr. Otter" is a fictionalized version of various animated television shows that the filmmakers used to watch as kids.