Martha Plimpton plays the older sister of Joaquin Phoenix a.k.a. Leaf Phoenix. In real life, she dated his older brother River Phoenix for nearly five years. River Phoenix and Plimpton also appeared in two movies together.
This movie is based on Ron Howard, Brian Grazer, Lowell Ganz, and Babaloo Mandel's experiences as parents.
In this film, Steve Martin plays the father of several children. In reality, Steve Martin did not become a parent until he was 67 years old, in 2012.
During filming, the cast became obsessed with playing the murder game (a game in which one person, who is the murderer, has to find a subtle way to kill other players simply by looking at them without giving themselves away as the murder). This is very apparent in the dinner scene where everyone is sitting around the table. If you watch everyone's eye movements, it's obvious they are playing the game.
In a Vanity Fair interview in March 2016, Dame Helen Mirren said she had never regretted not having children, except briefly when watching this film: "It was about the whole story of being a parent, and how it never stops, even when you're a grandparent. I realized I would never experience that, and for about twenty minutes, I sobbed for the loss of that, and the fact that I never experienced it."