Incorrectly regarded as goofs: Mary's glove appears to darken in the close-up when she reads the advertisement to Mr. Banks, due to the lighting.
Revealing mistakes: During the beginning of the "I Love to Laugh" sequence, when Uncle Albert says, "Loud and long and clear," his left hand goes transparent into the background. (From the 40th anniversary edition)
Continuity: Jane and Michael switch sides while they are holding Burt's hand when he walks them home.
Continuity: After Mary Poppins powders her nose black, her face in the next scene is clean again.
Revealing mistakes: Obvious stand-ins for Jane and Michael when Mary Poppins, Bert, and the children step onto a cloud which wafts them back down after exploring the rooftops (just before the "Step in Time" number).
Continuity: When Mary Poppins is tidying the nursery, the pictures straighten, but in the next shot, they are still crooked.
Continuity: Mr. Banks tears Jane & Michael's advertisement into eight pieces. Only eight pieces of paper go floating up the chimney, but at least twice as many are shown coming out of the top of the chimney.
Crew or equipment visible: When Mary and the children are sliding down the stairs you can see the equipment rolling along with them.
Crew or equipment visible: When Mary and the children are sliding down the stairs handrail as they go in front of the maid, part of the trolley is clearly visible on the left side of the boy.
Errors in geography: The robin that lands on Mary's finger in the "Spoonful of Sugar" sequence is an American, not British, robin.
Crew or equipment visible: When Mary first turns from the window with the singing bird perched on her fingers, the cables operating the bird are visible on the back of her hand.
Revealing mistakes: When Mary and Bert are dancing with the cartoon penguins, you can see Bert's legs and some of the "real" scenery through the cartoon penguins in some shots.
Revealing mistakes: When Mary Poppins pops out of the Banks's chimney, a cable supporting her can be seen against the sky.
Revealing mistakes: During the "Supercali..." song, when Bert and Mary sing "The biggest word you ever heard and this is how it goes..." Mary's head becomes slightly transparent and you can see the animation behind her. This goof might only be on the remastered 2004 DVD version.
Continuity: Bert places his hat inside the chalk drawing under a banner that reads, "Contributions Welcome" but after the rainstorm, his hat is underneath the drawing.
Continuity: During "Feed The Birds", Mary shakes the cathedral globe, and the birds flutter about. Less than five seconds later, the globe appears unshaken.
Continuity: In the opening credits, Mary is shown in a close up powdering her nose while sitting on a cloud. Her carpet bag is on her right and her umbrella is on her left. In a long shot, immediately after (which is animated) the carpet bag and umbrella are not present.
Continuity: Just before walking on the stairs made of smoke, they are walking single file on a rooftop in the following order: Mary, Jane, Michael, Bert. In the next close up shot, they are not in a line. They are in a group and Michael is in front of Jane.
Continuity: When Bert traces Mary's shadow on the sidewalk, the sunlight obviously comes from behind of Mary. However, when Bert stands up to greet Mary, the sun shines frontally into her face.
Factual errors: The two robin parents building their nest outside the children's bedroom window are both male.
Audio/visual unsynchronized: When Michael is locked in the closet while cleaning the nursery, the door opens for several seconds and we hear him yell "Let me out!" repeatedly, but his mouth doesn't move.
Revealing mistakes: The second time that all the Banks's furniture is moved by Admiral Boom's cannon, you can see a vase sitting on a column rock back and forth, and then be pulled back to its original position by a string.
Continuity: During the "Sister Suffragette" number, Mrs. Banks places a sash that says "Votes for Women" on Katie Nanna. First the words are on her right side, next shot on her left side, and in the final shot, back on her right side.
Revealing mistakes: During the 'Step in Time' number when the chimney sweeps pop out of the chimneys, in one scene all three sweeps are seen coming up behind the chimneys and not out of them.
Continuity: When Mary uses the tape measure on herself, she holds the tape horizontally to read it, however the close up shows the tape vertically with the words oriented that way.
Revealing mistakes: During the "I Love to Laugh" sequence, the strings attached to Michael are clearly visible in front of Mary's face when he first takes off. Later, the strings lifting Mary are visible when she joins the others at the table - showing that they are attached to her at the waist, just below her pocket.
Incorrectly regarded as goofs: At the end of the movie, the constable described the "missing" Mr. Banks as "about 6 foot 1". There is a common misconception that British people only use the metric system when in fact - particularly during the period depicted in this film - they use both.
Revealing mistakes: In the scene where the four carousel horses are lined up, you can see Dick Van Dyke's cable.
Continuity: When Mary Poppins is taking items out of her bag when she arrives, the pattern and colour of the bag changes.
Continuity: When the penguins bring Mary and Bert menus, the menus are pink. A moment later, Bert's menu is bright purple.
Continuity: In the penguin number Van Dyke's pants change to short legs and long crutch to long legs and short crutch.
Audio/visual unsynchronized: When Mr. Dawes Sr. comes out to see Mr. Banks and Jane & Michael, he's talking, but his mouth doesn't move.
Errors made by characters (possibly deliberate errors by the filmmakers): When Mrs. Banks bends to embrace the children (when the Constable brings the children back from the park), her head is turned to her left rather than looking at her children, obviously anticipating Mr. Banks' line which cuts off her embrace.