LA JOLLA — In a rehearsal room at La Jolla Playhouse Feb. 1, managing director Michael S. Rosenberg welcomed the press to a media preview of the Playhouse’s Broadway-aimed world premiere musical, William Finn and James Lapine’s “Little Miss Sunshine.” Lapine directs the musical based on the Academy Award-winning 2006 film. Rosenberg, who remarked that “Little Miss” is one of three world premiere musicals in the Playhouse season, then introduced Finn and Lapine, who commenced a discussion so amusing that, if recorded, would match any comedy routine in modern history. After saying “How lovely of you to come,” composer/lyricist Finn (“In Trousers,” “March of the Falsettos,” “Falsettoland” and “The 25th Annual Putnam County Spelling Bee”) said, “I’m sick of being depressed in the theater, either because the show stinks or because it is depressing. ‘Billy Elliot’ made me joyous. I wanted to write a show that’s delicious.” Lapine (all the above with Finn off-Broadway, as well as “Into the Woods” and “Sunday in the Park With George” with Stephen Sondheim) said, “Little Miss Sunshine’ is not slavish to the movie,” adding that the “rights people” gave them leeway to devise scenes of their own. As a result, “It’s a lot of the movie and a lot of us.” The movie and Lapine’s book concern the Hoovers. Grandpa (Dick Latessa) was kicked out of his retirement home. His son, Richard (Hunter Foster), is a struggling motivational speaker. Uncle Frank (Malcolm Gets) was dumped by his boyfriend; Richard’s teenage son (Taylor Trensch) has taken to silence; 10-year-old Olive (Georgi James), though neither beautiful nor talented, has entered a regional beauty pageant that occasions a trek from Albuquerque to Seal Beach. Long-suffering Mom (Jennifer Laura Thompson) perseveres, despite all impediments. Onstage road trips are not easy. The constant throughout the ever-changing scenario is the infamous Yellow Bus, which comes in full-size, half-size and remote-controlled mini. Among the musical numbers previewed, Latessa and James performed a duet that takes place on the eve of the pageant, in which Olive confesses she’s scared and asks Grandpa for reassurance. Grandpa answers, “You are the most beautiful girl in the world.” When Jennifer Caprio designs costumes, she always consults her actors. She asked James, a veteran Broadway actor (“Billy Elliot”), about her favorite color, to which James, actually 10, replied: “Rainbow.” James wore the fruits of a La Jolla Shores shopping excursion, a rainbow jacket serendipitously appliquéd with a yellow bus. Caprio, who designed costumes for Finn and Lapine’s “Putnam County Spelling Bee,” says of “Little Miss Sunshine,” “It’s been a fun challenge to figure out how to layer costumes for ensemble quick changes. In period dress you have gown layers, so it’s easy to hide, but with jeans and a t-shirt, not so much. “La Jolla is a great place to develop new work,” Caprio says, “because we’ve got the time, and we’ve got the sunshine.” And don’t forget Little Miss, Finn and Lapine. “Little Miss Sunshine” opened in previews Feb. 15 (critical opening March 4) and continues through March 27 in the Mandell Weiss Theatre, La Jolla Playhouse, 2910 La Jolla Village Drive. Information is available at www.lajollaplayhouse.org or (858) 550-1010.