Other mistake: On the first day of school, when Patty is starting to sit down next to Sandy, her reaction to sitting on the apple is way too early.
Other mistake: During the subway scene, when Dorothy, Tin Man and Scarecrow are trapped behind the red fence, there is no lock on the door in the fence. The door bounced once before falling shut, so it's probably not stuck. So how are Dorothy, Tin Man and Scarecrow unable to push it open?