Out of respect for Emily Blunt— who will play the flying nanny— Andrews "immediately said no," director Rob Marshall told Variety at the film's premiere.
Marshall said that the Oscar winner worried that by appearing in the film, it might take away from Blunt's performance, and her spin on the character.
"Julie was incredibly gracious, and we talked about it in a very general way but she made it clear right up front," Marshall claimed. "She said this is Emily's show and I want her to run with this. She should run with this. This is hers. I don't want to be on top of that."
During an interview for Variety's upcoming Actors on Actors issue, Blunt echoed a similar sentiment.
"She was very hands-off with the whole thing," she said. “She said to Rob, ‘Do you know what this is? This is Emily’s version of her and I don’t want it to be that she’s playing Mary Poppins the whole way through but then I come in and there’s like oh, but there’s the real Mary Poppins, you know?’"
While we won't be seeing Andrews in 'Mary Poppins Returns', original cast member Dick Van Dyke will make a cameo in the sequel, but not as Bert.