Blunt stars as Mary Poppins in the Disney sequel to the 1964 classic, expected to hit theaters in December 2018, while Miranda plays a lamplighter, Jack. Colin Firth, Meryl Streep and Angela Lansbury round out the cast, with Dick Van Dyke making a special cameo appearance.
ET caught up with the original Mary Poppins, Julie Andrews, in March, who called Blunt a "perfect pick" for the role.
"It is not a remake of the old Mary Poppins," Andrews explained, adding that she doesn't think she'll be a part of the film. "It is making all the rest of the stories that Walt Disney had stored in his vaults and now they have made a completely new Mary Poppins story."