Thanks to smart, refreshing movies like “Humpday” and “Your Sister’s Sister,” local filmmaker Lynn Shelton has become a darling of the indie film world.

But with the crossover potential of her latest film, “Laggies,” Shelton may be on the verge of some serious commercial success. It opens this weekend.

The film stars Keira Knightley as a woman in her late-20’s who panics at a marriage proposal. Realizing she’s not nearly as mature as her years would indicate, she escapes the pressure by befriending a 16-year-old girl, played by Chloe Grace Moritz.

In my interview, the friendly, easygoing Shelton talks about:

What the heck “Laggies” means and whether it’s a good or terrible movie title

How a film once set to star Anne Hathaway became a Keira Knightley vehicle

How Mad Men’s Jon Hamm helped Shelton cope with superstars

How we are all in some ways “laggies” at some point in life

How Keira Knightley spent her time in Seattle during filming (lived on a houseboat, shopped on Ballard Avenue)

Whether Shelton will be sweating out box-office returns opening weekend

What she’s done since finishing “Laggies” (including “The Mindy Project,” “New Girl,” and a new TV pilot)

What she’s got in the pipeline (three film projects, including her biggest budget by far.)