To avoid accidentally copying Julie Andrews's version of Mary Poppins, Blunt based her interpretation on the P.L. Travers novels, as well as the 1940s screwball comedy His Girl Friday. "[Mary Poppins] thinks she's better than everyone – which she is... I think the pace at which she speaks and the way in which she speaks is a way to hold people at arm's length and not over-sentimentalise moments."
One of Blunt's favourite parts about filming Mary Poppins Returns was sharing a few off-camera moments with returning star Dick Van Dyke. "Between takes, he'd put his hand on my arm and sing, 'It's a jolly holiday with Mary'."