Chelsea Handler, Mary McCormack and Charlize Theron

The BFFs were among the loudest marchers in Park City, Utah, where many celebs were participating in the rally as it coincided with the Sundance Film Festival. Handler also posted a video on Twitter, explaining why she was walking with "two of my besties," Theron and Mary McCormack. "We're here in Sundance and we're ready to march because we're going to get loud and proud," she explained, adding, "Everybody's going to stand together and we're going to come together. There's a movement happening! Get with it!"
Getty Images