Mary Poppins is a character from the book and film.
When Shary Bobbins introduced herself to the Simpsons, Homer asked if she said "Mary Poppins". Shary repeated her name, saying she was an original creation, like Rickey Rouse or Monald Muck. When Homer started to use items and then return them, he said that he can "Mary Poppins" himself to work with an umbrella that he opened.
Episodes: Simpsoncalifragilisticexpiala-D'oh!-cious (Mentioned)