Dakota Fanning made Vulture's list of Eight Clean-Cut Stars Who Got Wild at Sundance — but was it actually her butt we saw streaking down the beach in Naomi Foner's Very Good Girls? We posed the fanny question to Fanning herself, at a premiere party for the film this week: “It’s, like, complicated," she told us at the Nur Khan pop-up in Park City. "It’s kind of mine." What she means, Foner explains, is "they weren’t actually naked." They were wearing a bathing suit, but "they painted the bathing suit out — it’s CGI." Fanning's co-star Elizabeth Olsen was willing to admit that she called in backside backup altogether. “It’s a double and then they CGI-ed the stuff in the water," she told us. "But I think my double has a great ass."