Continuity mistake: When Whoopi first takes over the choir, she asks the sisters to stand according to their singing voices. She asks where the sopranos are, and several women on opposite corners of the grouping raise their hands. She asks them to all move over to the left group, but only one of the two women on the right side actually does so.
Continuity mistake: When the choir are singing the first song that Deloris helps them with, Sister Mary Robert gains confidence and sings louder. Toward the end of the song, she puts her hands together in a praying gesture while she is singing loudly, but in the next shot her arms are by her side.
Continuity mistake: When Deloris is on TV, we see her lift a stuffed rabbit to try and hide her face, she then gives it to Mary Robert and lifts the kid to her face but when Eddie says "I'm gonna kill her. I'm gonna kill her myself", if you look on the TV, you can see her doing the exact same thing again.