One small step for Sydney Sweeney, one giant leap for fashion. The actress launched a style supernova at her space-themed birthday bash, dressing in a dazzling star-spangled mini dress. Sweeney's futuristic ensemble - a shimmering constellation of crystals, metallic mesh and three-dimensional appliqués - was a time-traveling tribute to The Blonds' Spring/Summer 2009 collection that was famously worn by pop icon Britney Spears during her Circus era. "Welcome to planet syd 👽🛸🚀," Sweeney wrote via Instagram on Monday, September 29.