From left: Julianne Hough, Carrie Ann Inaba, Derek Hough, Tom Bergeron, Bruno Tonioli, Alfonso Ribeiro Disney/Eric McCandless Dancing with the Stars on Tuesday threw the mother of all reunions to celebrate 20 years on ABC. After a star-studded episode featuring past pros like Edyta Śliwińska, Max Chermkovskiy, Charlotte Jørgensen, Brian Fortuna, Lindsay Arnold and Anna Trebunskaya and past contestants like Kristy Yamaguchi, Kelly Monaco, John O'Hurley, Mirai Nagasu, Amy Purdy, Chris Mazdzer, Noah Galloway, Shawn Johnson and Gilles Marini, a birthday bash was held on an adjacent stage at LA'...