- California Doubling: The scenes that took place in Redondo Beach, California, were actually filmed in Ventura, California. None of the freeways near Redondo Beach lead to the beach.
- Cast the Expert: The girls at the pageant are real life pageant competitors (wearing their actual costumes). Ew.
- Dawson Casting: Dwayne is 15 and was played by 22 year old Paul Dano. Also ties into Playing Gertrude, as Toni Collette is only 12 years older than Dano and is playing his mother.
- Enforced Method Acting: During the Corruption of a Minor scene, Alan Arkin deliberately told Abigail Breslin to tune up the volume of her CD player so she won't hear the Cluster F Bombs and Precision F Strikes.
- The directors also had the main cast actually drive around in an old VW bus for a while, so they would understand what it was like being stuck with one another.
- Fake American: Toni Collette is Australian.
- In Memoriam: The film was dedicated to Rebecca Annitto, the 14-year-old niece of producer Peter Saraf, who was killed in a traffic accident in 2005. She appeared as an extra in scenes at Pann's Restaurant and the convenience store.
- Inspiration for the Work: The catalyst for the movie was a comment by Arnold Schwarzenegger that the people he hates most in the world are losers. The screenwriter Michael Arndt took offense to this comment, believing that everyone is a loser in some way, but that doesn't make them a bad person. He wrote the screenplay to refute that kind of black-and-white thinking.
- Playing Against Type: Steve Carell, whose type really hadn't been established yet, but has not since played a role this subtle and understated.
- Star-Making Role: For Abigail Breslin.
- What Could Have Been:
- Thomas Haden Church was offered the role of Richard but turned it down. He later regretted this decision. Alec Baldwin and David Duchovny were also considered.
- Bill Murray was the original choice to play Frank, the second being Robin Williams.
- Donald Sutherland almost had the role of Grandpa Edwin Hoover before Alan Arkin was cast.
- Dwayne was originally supposed to have a Mohawk.
- Word of God: Dwayne is Sheryl's son from a previous marriage, making him Olive's half-brother and Richard's step-son.
Trivia / Little Miss Sunshine