Over the weekend, many celebrities celebrated Halloween and dressed up to get into the spirit. Kim Kardashian transformed into her idol, Cher, for Halloween. Her BFF Jonathan Cheban was Sonny. Her transformation caught the attention of Cher herself, who tweeted: “You look beautiful.” The mom of two wasn’t the only star channeling another star for Halloween. Olivia Newton-John's character from Grease was the inspiration for model Joanna Krupa's costume.