I've written about this more than a few times. I think a post could be added to one of the stickies about the lesser known or non-publicized entertainment at
Disneyland. [including the entrance show, castle show, firehouse show, musical chairs ]
The "Mary Poppins show" is not distinctly listed anywhere by Disney. It takes place in front of the castle but is
not what is referred to on this board as "the castle show".
It features the Pearly Band, with Mary, Bert, and some kids invited to participate.

Mary Poppins admires Bert's hop by
perlster, on Flickr