Continuity mistake: When Max Bialystock is singing "Along came Bialy", and the old ladies start coming out of the apartments, the first lady who comes out isn't there in the next shot.
Revealing mistake: Just after they dump the tacks out of the window, the Russians' car flies up into the air in a really quite impressive car crash. Just before it flips over though, you can see the huge ramp put in front of it. (00:32:20)
Visible crew/equipment: As Zeebo is kissing Tanya, the device used to make his ears wiggle is briefly visible.
Continuity mistake: During the ice show Smoochy gets crowned by the fairy who flies in from above. Right before he sits down at the desk to read the "Smoochy Hits #1" issue of Variety, the crown falls off and rolls away across the ice. When he's sitting at the desk, the crown is back. (01:32:51)
Continuity mistake: When Mumble is still a baby, his "bowtie" does not appear until Boss Skua has him pinned down under his foot. Then shortly after, it disappears again, only to reappear when Mumble falls into the crack in the ice.
Continuity mistake: In one scene when Hudson and Andrews enter the vestibule of her house, Rock can clearly be seen to have "mutton chop" sideburns. However, once inside the house, they're gone. When he goes back outside, they're back.
Other mistake: The catapult on the battlements Jean uses to evict the castle guards is rather curious. First, there is neither a bow nor any torsion to 'power' the weapon, and secondly it just seems to cock itself, right after each shot. All that Jean does is pull the lever and none of her diminutive helpers stand by for any cocking work whenever the catapult arm is shown.
Continuity mistake: Towards the end of the movie during the play, Kelly goes backstage during intermission, and her hairstyle and color has changed. (According to DVD commentary, it was a pick-up scene and she had already started filming Spider-Man. That's why her hair was now red. Still a mistake, but there's the explanation.)
Factual error: Jane Russell and others say several times that they are sailing from New York to Paris. They might have been sailing to Cherbourg or Le Havre, but they couldn't have been sailing to Paris. The producer seems to assume that if they referred to Le Havre or Cherbourg, viewers wouldn't be able to sort it out.
Factual error: Towards the end of the song "Out There" Quasimodo climbs onto the large spire on the roof. That spire was added in the 19th century and thus didn't exist when the movie was set.
Continuity mistake: As Shirley Jones is singing "In love with Me" at one point, she's sitting down, and is slouching back. The shot changes to the side, and she's sitting up straight, and is much higher against the counter than she was. Her hands have changed position as well, she's no longer holding onto the cup she had in her left hand. (01:19:55)
Continuity mistake: When Dorothy Lamour gets out of the water and confronts Bing Crosby and Bob Hope, she's supposedly naked and covering herself with leaves. But you can see the flesh colored bathing suit she's wearing bunch up at the hips while she moves. (01:10:22)
Revealing mistake: In the scene where King Arthur expounds on the joy of his kingdom, he has a Band-Aid on the back of his neck. (00:21:00)
Continuity mistake: After their first number, Ted and Jim are in their dressing room, Jim is buttoning his left cuff and then pulls down his right sleeve. In the next shot, he does this again.
Visible crew/equipment: When Groucho enters the rehearsal area, the shadow of the camera is visible behind him.
Other mistake: After talking to his own mirror image when guarding his house from the "Heffalumps and Woozles", Pooh turns around counter-clockwise. This should mean that his mirror image would turn clockwise but it ALSO turns counter-clockwise. (00:35:55)
Other mistake: The snow globe from the original is in the loft in the new film, but in the original film, as Mary was leaving the Banks house while they flew a kite, she packed it in to her carpet bag.
Continuity mistake: When El Khobar is romancing Margot, he keeps his face covered with a veil so she won't recognize him as her professor. As Margot is approaching him while they are singing the desert song, he pulls they veil over his face and you can see the tan lines of a wedding ring.
Audio problem: When Galleria is playing the piano by herself at school, it's obvious she really isn't playing. Her hands are moving way too slow for some of the parts and at the end, her hands are playing very low on the bass notes when the notes heard are in middle-low C range.
Continuity mistake: In the scene where Judy Garland and Fred Astaire go to the nightclub to see Ann Miller, Ann invites Fred to come up and dance with her. When she is dancing by herself, she is wearing red high heels. When Fred comes up, she is wearing red flats.