Continuity mistake: In the audience, Carl's parents are shown sitting in the second row behind Jimmy's and Cindy's parents. In some POV shots of the stage, however, they're still in the second row but are sitting behind Corky Shimatzu, who is sitting on the opposite side of the theater from Jimmy's and Cindy's parents.
Revealing mistake: Right after the scene with the witches, Cindy disguises herself while offering coffee to the producer Corky Shimatzu. However, besides the Groucho Marx glasses and nose, she is wearing her normal outfit when a few minutes earlier, she was wearing her witch outfit, had green makeup on her face, and her hair was a completely different style. Then a few minutes later, she goes back to her play costume. That makeup must have taken at least an hour and would take just as long to remove it. Yet she changes from and back to it in a matter of minutes.