Chiwetel Ejiofor signed “Doctor Strange” posters and Julianne Moore signed a photograph of herself in a golden Viking costume in “The Big Lebowski” as fans mobbed them and other celebrities in Park City Friday.

Ejiofor, who also starred in “12 Years a Slave,” is making his feature debut as a writer and director with the Sundance Film Festival Premieres film “The Boy Who Harnessed the Wind,” which tells the story of a 13-year-old Malawi boy who decides to build a wind turbine in order to save his village.

The movie — written by, directed by and co-starring Ejiofor — has been named the winner of the Alfred P. Sloan Feature Film Prize, given to a Sundance movie with a science theme.

Moore and Michelle Williams star in “After the Wedding,” which screened Thursday on the festival’s opening night, and both were among the celebrities fans spotted on Park City’s Main Street Friday. Super fan Stuart Graves, known for his pursuit of selfies with stars, tried to maneuver himself into a portrait with Moore.

Others spotted included Jada Pinkett Smith, David Crosby, Billy Crudup, Peter Skarsgaard, Martin Starr, Malin Akerman and Xabiani Ponce de León.

Skarsgaard plays a New York City “house tuner” who calibrates the sound in people’s homes to adjust their moods in “The Sound of Silence.” Akerman appears in “To the Stars,” the story of a shy farmer’s daughter (Kara Hayward, from “Moonlight Kingdom”) who begins an intimate friendship with a worldly new girl (Liana Liberato) under the gaze of her small-town neighbors in 1960s Oklahoma.

Starr appears in the drama “Honey Boy” with Lucas Hedges (“Boy Erased”) and Shia LaBeouf, who star as a child TV star and his father, a hard-drinking ex-rodeo clown. De León stars in “This Is Not Berlin” as a misfit teen invited to a mythical nightclub.

The festival runs Jan. 24-Feb. 3 in Park City and at venues in Salt Lake City and the Sundance resort.