Celebrity style: 1970s inspiration Demi Lovato at the 2018 Billboard Music Awards at the MGM Grand Garden Arena in Las Vegas on May 20, 2018. (Photo by Kevin Mazur/WireImage) Kesha at the 2018 Billboard Music Awards at the MGM Grand Garden Arena in Las Vegas on May 20, 2018. (Photo by John Shearer/Getty Images for dcp Ciara at the 2018 Billboard Music Awards at the MGM Grand Garden Arena in Las Vegas on May 20, 2018. (Photo by Kevin Mazur/WireImage) Andra Day at the 90th Annual Academy Awards at the Dolby Theatre in Los Angeles on March 4, 2018. (Photo by Eric McCandless/ABC) Tiffany Haddish at the 90th Annual Academy Awards at the Dolby Theatre in Los Angeles on March 4, 2018. (Photo by Rick Rowell/ABC) Leslie Mann at the 29th Producers Guild Awards presented by Cadillac at the Beverly Hilton in Beverly Hills, California, on January 20, 2018. (Photo by John Salangsang/Invision for Producers Guild of America/AP Images)