With Dick Van Dyke coming back in Mary Poppins Returns, a lot of people were wondering why the original Poppins herself Julie Andrews wouldn't be appearing in the movie. As it turns out, Andrews didn't want to steal any of Blunt's thunder in the movie.
Blunt had told Variety in regards to Andrews' decision:
"[Andrews] said to Rob [Marshall, the director], '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?'"
Producer Marc Platt also reveals that there was never really any decision to have Andrews appear at all. Platt explains:
"She wasn't supposed to be in it at all… But she's a friend of Rob's and a friend of ours and a big fan of Emily Blunt and has been lovely since day one about how this is Emily's turn and how happy she is for her…And it's Emily's turn."
Though I'm sure some people will be bummed that Andrews won't be appearing, I think the showrunners made a good choice in not having Andrews's shadow cast over Blunt in the film. After all, if she's not playing an older Mary Poppins, I think it would be weird to just have her as a random supporting character. They could try and have Andrews' Poppins come back from the future (because magic) but that's a bit too Star Trek 2009.
On another note, you could still catch Andrews in a movie this December since she's set to appear in James Wan's Aquaman.
Catch Mary Poppins Returns in theaters Dec. 19.