The sleeper hit of summer.

But don't ask the directors of Little Miss Sunshine how their road-trip flick became the little movie that could. They weren't sure the movie would get made, let alone hit the top 10.

"It's such a quirky story," says Jonathan Dayton, who with wife Valerie Faris directed Sunshine, their first feature. "That's not always easy to sell to studios, or to know if you're going to reach audiences."

But Sunshine has managed to finally give summer its word-of-mouth hit. It was the No. 3 film of the weekend, taking in $7.5 million in its fifth week and raking in $23 million so far.

"It's a miracle we're even talking about this," Dayton says. "For a while, we thought for sure (the movie) was dead in the water."

Written in 2001 by Michael Arndt, a former assistant to Matthew Broderick, the script languished for two years.

When Focus Features finally picked it up, there were debates over how to cast the film about a dysfunctional family trying to get its youngest member to a child beauty pageant. Focus wanted an A-list star who would drive box office overseas. Dayton and Faris wanted more of an ensemble piece.

Creative differences kept the movie in limbo another two years, until producer Marc Turtletaub bought the script back from Focus for $400,000 and decided to pay for the $8 million movie himself.

That freed Dayton and Faris to choose the cast they wanted, including Greg Kinnear as a father struggling to sell a self-help book, Steve Carell as a suicidal uncle and Alan Arkin as a heroin-snorting grandfather.

And while those characters may not seem like the linchpins of a hit film, Sunshine capitalized on several events:

•Carell's surging fame. The filmmakers signed Carell before 2005's The40-Year-Old Virgin became a comedy smash.

•Teaser screenings. Executives at distributor Fox Searchlight made big successes of small films Napoleon Dynamite and Garden State. After snapping up Sunshine at the Sundance Film Festival, the studio arranged 220 free screenings — second only to Dynamite— and handed out 16,000 yellow t-shirts with the film's VW van on them. "We knew we had a movie people would talk about," says Searchlight's Steve Gilula. "We just had to get the talk started."

•Great reviews. Critics can make or break small movies. And 93% of critics liked Sunshine, according to rottentomatoes.com.

•Relatability. The filmmakers are surprised that the character most moviegoers relate to is Dwayne (Paul Dano), a teen so fed up with his family that he hasn't spoken for nine months. "This family is dysfunctional to the extreme, but I think everyone relates to a family under stress," Faris says. "We knew there would be an audience for this movie. We just never imagined it would be this big."

Enlarge By Eric Lee, Fox Searchlight Little Miss Sunshine, a dark comedy starring Toni Collette and Greg Kinnear, is this summer's surprise box-office hit.