Maggie Gyllenhaal has signed on for Nanny McPhee and the Big Bang, a sequel to the 2006 film about a Mary Poppins-like governess played by Emma Thompson, reports Variety. Also joining the cast: Maggie Smith, Rhys Ifans (Notting Hill) and Asa Butterfield (The Boy in the Striped Pajamas). Ralph Fiennes is in discussions for an uncredited cameo. Thompson is also exec producing and writing the screenplay, based the Nurse Matilda books by Christianna Brand. The production, to be helmed by first-time feature director Susanna White (Bleak House), is set to start in the summer.