At various times throughout the film, Mrs. Collins' pink scarf alternates from her shoulder to her arm, changing positions occasionally.
When Dr. T. catches Bart, his mother and Mr. Zabladowski trying to escape (after the fight with the twins Johnson and Whitney), he is wearing a lavender coat with black trim when he first appears and says, "I, on the other hand, am inclined to doubt that." For the rest of the sequence, he wears a black coat with a pink treble clef and white stripes representing the five-line staff.
When Johnson and Whitney are first seen moving around on roller skates in the Piano Yard, Bart is seen poking his head out from behind a small pink piano in the background. In the context of the film's plot, Bart is supposed to be hiding at the top of the stairs to his mother's office.
When Bart hides in the large vase, he places a bunch of flowers on his head. When the guards lift him from the pot, they are on his head. In the cut shot moments later, the flowers have disappeared.
In the first scene in the Terwilliger Institute, Dr. T. buttons his jacket closed after putting his baton away. Immediately after in the long shot, his jacket is open, then in a closer shot, it is buttoned again.
As Bart descends from the top of the ladder, he casts a shadow against the sky.
While Dr. T. is sleeping, Bart climbs up to get the key to the safe that is in the metronome above the bed. When the camera shows a close-up shot of Bart, Dr. T. is facing the left edge of the bed and is face-to-face with Bart. When the camera shows a distant shot, Dr. T. has rolled over to the right side of the bed. In the next close-up shot, he is again facing the left edge of the bed and is face-to-face with Bart.
It is clear in some scenes in the film that Bart is not really playing the piano: sometimes he misplaces his fingers, sometimes he does not move his fingers correctly, and sometimes he even fails to press down on the keys.
Throughout the whole of the instrumental scene of the film with the various performers, there are so many continuity, revealing and audio/video goofs that it would be impossible to record them all.
When Bart climbs the huge ladder to escape the guards and then jumps off of the ladder, you can clearly see a thick wire holding him up.
About 17 minutes into the film, Dr. T. tells Mrs. Collins that "your son dares to flaunt my authority" (the correct word would be "flout").