Corrected entry: In the scene were Mary Poppins is moving in and taking the hat rack, plant, lamp, etc out of her carpet bag, when she takes out the hat stand you can visibly see the shadow of a crew member to the far right of the picture.
Corrected entry: At the beginning of the movie, when we first see Admiral Boom's house, we see that the Banks house right next store is also a 2 story home. However, the children's nursery is on the third floor (up 2 flights of stairs). There is no third floor.
Correction: You see later on in the movie that when they go up to the first floor there is only one door which is probably a closet and wouldn't have a window. So it wouldn't really count as a floor so there is just 2 flights of stairs up to the second floor.
Corrected entry: During the clean up of the nursery scene, a group of hats, including Jane's straw hat with the brown velvet ribbon, fly into a closet and hang on hooks. Above them is a shelf with boxes. When the clean up is complete and the children and Mary Poppins are getting ready to go out, Jane retrieves the same hat, now on the shelf instead of the hooks, and the boxes that were on the shelf are gone.
Correction: When Jane cleans up the hats, the hat with the brown ribbon has a round top and the hats are placed in a closet that has a wall on the right side making it seem like there is space between the corner of the wall and the closet, when Jane takes out the hat, its not the same hat as the first, the hat has a flat top with a red burgendy kind of color ribbon and the closet is placed at the corner of the room.
Corrected entry: Some of the rockets in which the captain's assistant puts into the cannon have duct/masking tape around them. Duct/masking tape wasn't invented then.
Correction: While it's true that masking tape didn't exist in 1910 (it coming in the 1920s), an early version of "duck tape" was in use in America in the early 20th century. It's plausible that this was in use in London 1910 but duct tape as we now know it dates from WW2 and is different from early "duck tape".
Corrected entry: Dick Van Dyke portrays both Bert and the elder Mr. Dawes.
Correction: Even if you can't tell while watching (pretty unlikely as you can easily see it's him), then he is listed in the credits.
Corrected entry: In the scene after they have finished cleaning the children's room and are leaving to go to the park, half of one of the beds is missing.
Correction: The bed that is visible is the far one (from the camera). The height of the folded bedspreads creates an optical illusion. The bedspread nearer to the camera appears to be on the farther bed, but a close look shows that it is not. The bed closest to the camera is just out of the shot.
Corrected entry: Near the end, just before "Let's Go Fly A Kite", when Mr Banks has returned home his detachable collar is detached on his left-hand side in shots from the front but not from the back of him.
Correction: There is no problem with his collar at all.
I just watched this and indeed the collar is popped out on one side.
Corrected entry: When the cook attacks the chimney sweeps, she uses a non-stick frying pan. Non-stick frying pans weren't invented until the 1950s, and the movie takes place in the 1910s.
Correction: Upon closer inspection, the pan is in fact not non-stick. But instead carbon steel, which would be appropriate for the time period.
Cast-iron would be most appropriate for 1910. Carbon steel certainly existed at the time and was used in the manufacture of high-end swords, sawmill blades, cutlery, razors and the like, but would be prohibitively expensive for the manufacture of frying pans for the general consumer.
Correction: That's Michael's shadow.