Throughout the movie, the Cromwell's use a spell to null the effects of others' spells. While originally, the incantation is, "Magicus Fixus", it changes during the confrontation with Ethan's dad to, "Magico Faxum".
When Ethan was trying out for the play, Aggie told Marnie that she was offered to cast in Shakespeare's original play. But in Shakespeare's time, the ladies' roles are played by men because women are forbidden to act in a play.
When Gwen closes the cabinet after putting the Grasshopper Flakes in the cabinet, the fake "glass" comes out of the cabinet for a moment.