Screenwriter Michael Arndt originally set the road trip on the East Coast, from Maryland to Florida, but changed it to New Mexico to California for budget reasons.

Arndt initially planned to shoot the film himself using a camcorder before giving the screenplay to producers, who eventually sold it to Marc Turtletaub for $250,000 in 2001.

Focus Features wanted to shift the story's focus to the character Richard Hoover and fired Arndt when he disagreed, replacing him with another writer for four weeks before rehiring him after a studio regime change.

After Focus Features dropped the project in 2004, producer Marc Turtletaub personally paid $400,000 to buy back the rights and then financed the entire $8 million budget himself.

Arndt included the character Stan Grossman as a direct tribute to the Coen brothers' film Fargo.

The role of Frank Ginsburg was originally written for Bill Murray, and there was also studio pressure to cast Robin Williams, before Steve Carell, then still relatively unknown in Hollywood as a Daily Show correspondent, was cast a few months before filming.

Casting directors traveled to 'every English-speaking country' to find the actress to play Olive, ultimately choosing six-year-old Abigail Breslin through an audition.

Paul Dano was cast as Dwayne two years before production began and, to prepare for his character's vow of silence, took his own vow of silence for a few days.

Arndt rewrote the film's ending just six weeks before its Sundance premiere, and the new ending was shot in December 2005 during post-production.

The film is dedicated to Rebecca Annitto, an extra in the diner and convenience store scenes and niece of producer Peter Saraf, who died in a car accident on September 14, 2005.

Five Volkswagen T2 Microbuses were used for filming, three with working engines and two mounted on trailers for different camera setups.

The van's mechanical problems in the film—the broken clutch, stuck horn, and detached door—were based on real issues writer Michael Arndt experienced with the same type of vehicle during a childhood trip.

Greg Kinnear described the driving scenes as dangerous, recalling going about 50 mph in the vintage van with no side airbags while a camera truck sped alongside them.

During scenes where Alan Arkin's character swore excessively, Abigail Breslin wore headphones so she couldn't hear the dialogue, mirroring her character's obliviousness, and only learned what was said when she later saw the finished film.

All the girls playing pageant contestants, except Abigail Breslin, were real-life beauty pageant veterans who performed the same routines and looks from their actual competitions.

To make Breslin appear 'plump' as her character, she wore a padded suit during filming, and she spent two weeks rehearsing her final dance routine with a choreographer.

The directors discovered the band DeVotchKa's music after hearing their song 'You Love Me' on a Los Angeles radio station, and were so impressed they bought cast members iPods loaded with DeVotchKa albums.

The film's score, largely adapted from pre-existing DeVotchKa songs, was ruled ineligible for Academy Award consideration due to the proportion of previously written material used.

Arndt's original screenplay called for Prince's song 'Peach' during the pageant scene, ZZ Top's 'Gimme All Your Lovin'' was used during filming, and the final film used a remix of Rick James' 'Super Freak' suggested by the music supervisor during post-production.

Fox Searchlight acquired worldwide distribution rights for $10.5 million plus 10% of gross revenues within hours of the film's Sundance premiere, one of the biggest deals in the festival's history at the time.

A controversy arose when the Academy of Motion Picture Arts and Sciences limited Best Picture producer credit to three of the film's five producers, excluding Albert Berger and Ron Yerxa despite their significant contributions, prompting the Academy to later allow exceptions for films with more than three producers.