The "Chained to the Rhythm" singer swish swished her way down the red carpet at the Stella McCartney women’s and men’s Autumn Winter 2018 collections presentation in Los Angeles on Tuesday.
Perry rocked an over-sized crimson piece from the designer that featured a bold, ruffled asymmetrical neckline, which she paired with a matching lip, smoky eyes and black-and-neon pink shoes.
"I designed it for her, so it's good to have a friend like me," McCartney joked to ET as the pals walked the red carpet together.
"It is," Perry, 33, agreed, noting that she could take home food in the frock's pockets -- which McCartney had promised there would be. "It's so comfy. I love it so much... I've got, like, so many other layers underneath this."
As for the other designs that would be seen at the launch, McCartney, 46, stressed that she's "a designer for real women," preferring to make clothes that are "sustainable and responsible." But it might be her personality that Perry is drawn to as much as her clothes! "She's one of the more approachable, funny, down-to-earth, real people in that industry," the GRAMMY-nominated singer told ET.
"I'm excited to actually find a person that we can elevate and give a great kind of platform to," she explained. "I think there are some people that are feeling a bit down and out about the United [States], so I think it would be great to show that the good ol' American dream still does exist, and it's about talent, hard work and timing."
Perry wasn't the only famous face who came out to support McCartney. Kate Hudson and Goldie Hawn made it a mother-daughter date night, and Paris Jackson, Christina Aguilera, Olivia Munn, Rebecca Romijn, Kate Bosworth, Billie Lourd and Amy Poehler were also among those in attendance.
And there was one very special guest above all: the designer's dad, Paul McCartney! The Beatle told reporters he was "super proud" of his daughter as he hit the carpet with wife Nancy Shevell.
For more on Perry and Idol, watch the video below.