Someone restrain Elton John — his good pal Madonna's lip-syncing again. The Material Woman is heading up the voice cast of French filmmaker Luc Besson's big-budget computer-animated Arthur pic, according to The Hollywood Reporter. Based on Besson's series of children's books, the English-language film follows a 10-year-old boy named Arthur who goes in search of a hidden treasure. Madonna will play his sidekick, Princess Selenia. Okay, Elton — breathe.