These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
She even gets a song about it in the stage musical. She's Practically Perfect, after all.
Base Breaker: Mary Poppins' strict and pompous behavior has won over some readers, who feel thankful that her personality doesn't taste like diabetes, and turned away others, who find her unreasonably heartless.
Sequelitis: The books seem to get less creative as the series progresses, at least to some readers.
Disney's movie and play
Adaptation Displacement: How many of you can actually say that you saw the movie with prior knowledge that it came from a book?
There are also who think Mary Poppins is an irresponsible, dangerous drunk. She supernaturally "blows" the competition away for the job, then takes her charges to play with a homeless man. After giving them cough medicine. That tastes like rum to her.
Some people think she gives off a cold and dismissive feeling and would not actually be very successful with real children, like she was in the movie, in real life.
Given how dismissive she is of everyone she meets, except when they fall about praising her, Mary Poppins is some kind of high-functioning sociopath.
And yet, Pamela Travers (the author of the books) thought the Mary Poppins of the film was too nice. Fans of the books often agree with her.
On the opposite end, people are split if Burt is totally mundane if charming, or if he's of the same breed of magical that Mary is (albeit in a much lesser capacity). The musical seems to support the latter.
Chim chiminey chim chiminey chim chim cheree, a sweep is as lucky as lucky can be! Chim chiminey chim chiminey chim chim cheroo...
Just...A... Spoonful of sugar helps the medicine go down, the medicine go dow-own, the medicine go down! Just a spoon full of sugar makes the medicine go down, in the most de-liiiiiiiight-fullllll waaaaaaaay!
Feed the birds, tuppence a bag. Tuppence, tuppence, tuppence a bag! Feed the birds, that's what she cries, while overhead her birds fill the skies!
Famously, this song was a favorite of Walt Disney. Whenever he visited the Sherman brothers, he would say "play it". They would already know he meant "Feed the Birds" and play it for him. Even at his funeral.
Let's! Go! Fly a kite! Up! To! The highest height! Let's! Go! Fly a kite, and send! It! Soaring!
Supercalifragilisticexpialidocious. Even though the sound of it is something quite atrocious. If you say it loud enough, you'll always sound precocious....
I love to laugh! Loud and long and clear! I love to laugh! It's getting worse every year...
Step in time! Step in time! Step in time! Step in time! Never need a reason, never need a rhyme! Step in time! You step in time!
Heck, even Mr. Banks' song, "The Life I Lead", is catchy!
Interestingly, the first song of the movie, "Sister Suffragette", is one that practically no one seems to remember.
From the musical: I'm Practically Perfect in every way. Practically Perfect, that's my forte. Uncanny nannies are hard to find. Unique yet meek, unspeakably kind...
Ensemble Darkhorse: Miss Andrew, the anti-Poppins, seems to be this in the stage version. In the film version Mrs Banks is extremely beloved by fans.
Everyone Is Jesus in Purgatory: Mary Poppins could be an angel or even some kind of goddess, given her "perfection" and the fact that she comes from the sky. Also, note the religious overtones of "Feed the Birds."
Fridge Brilliance: Why does everyone in Bert's chalk drawing world love Mary so much? Because he does too.
Julie Andrews and Dick Van Dyke disagreed on the radio talk show Hollywood Spotlight Microphone over the possibility of Mary Poppins getting a Broadway adaptation. Van Dyke strongly supported the possibility, while Andrews felt that it wouldn't work, as the film's effects wouldn't work on-stage. Both have seen the stage production since.
From "I Love To Laugh", "Some only blast - others they twitter like birds."
Magnum Opus: The culmination of all the innovations and progressions Walt Disney made during his filmmaking career.
Memetic Badass: Mr. Dawes Sr. became this among italian Youtube Poopers, it all started with this (title roughly translates in 'Old Man Dawes will kick your ass!').
Purity Sue: A rare positive example, helped by Andrews's Academy Award winning performance, making Mary come across as a three dimensional character.
Rewatch Bonus: Watch the movie again after having seen Saving Mr. Banks and try not to cry at all the scenes involving Mr. Banks' Character Development, the ending, and the scenes which have more resonance now that the reason and meaning behind them is made clear. Just try. Heck, even the innocuous not-quite-Villain Song "Fidelity Fiduciary Bank" becomes outright disturbing when you remember Colin Farrell (maybe?) trying to sing it while drunk.
So Bad, It's Good: Not the movie itself, mind. But rather, Dick Van Dyke's accent. Dick van Dyke's accent was the result of his trying, and failing, repeatedly, to do a good Cockney accent. When it turned out he could only do a bad Cockney accent, he decided to make it hilariously bad.
Tastes Like Diabetes: The WHOLE animated sequence, but particularly "Jolly Holiday" and the scene with the barn animal choir.
They Just Didn't Care: The Masterpiece and Gold Classic DVDs trim the top and bottom of the picture. The 40th and 45th Anniversary DVDs show the full height, but snip a little bit from the left and right sides. The 50th Anniversary edition, however, doesn't appear to have any cropping at all.
Unresolved Sexual Tension: Mary and Bert seem to have been a couple sometime in the past, which rises to the surface during their outing in the country. ("You haven't changed a bit!")
Wangst: Really, Uncle Albert, feeling upset about your guests having to leave soon is one thing, but having a crying fit about it is another thing altogether.
What Do You Mean, It's Not Didactic?: Some critics and academics have argued that the film encapsulates the societal shift of its time, with Mr. Banks representing the passing of the stuffy 1950s and Mary Poppins representing the arrival of the carefree 1960s. Thomas Schumacher has stated that the contrast between generations is represented in the stage musical by the character's outfits. George Banks, Miss Andrew, and most of the adults represent the older up-tight Victorian era while Mary Poppins, Bert, Mrs. Corry, Northbrook, and a few others represent the much looser Edwardian era.