Before Sister Mary Clarence enters the music room for the first time, the students can be heard telling the same "Yo Mama" jokes through the door that they tell once she enters.
In the final performance of Joyful, Joyful, as the camera crane hovers over the act then changes to a shot of Whoopi Goldberg conducting and dancing with the group you can clearly see a camera move into the dancers behind Whoopi before it cuts to the next shot.
At the competition, Mary Roberts's hands are up on her face when she hears the news that sister Mary Clarence is a fake. In the next shot they are down by her sides.
Sister Mary Clarence: [after Maria has said she doesn't know the words of a song and her classmates snicker]
Hey, hey - excuse me! It is NOT Maria's fault, that she does not know that Mary had a lamb. It is not - and I say this to you - it is *not* Maria's fault. Because maybe, MAYBE where Maria came from, Mary had a dog! Or a lil kitty cat! Or a little bald headed brother named Bart! It is NOT her fault and we're not going to tell her it is, are we? No, we are not!