When the cast sings onstage, the spirited children sing along in the wings. Isaac and Maria also frolic in the fancy box seats on the left side of the theater. They run up and down the stairs that lead to the basement dressing rooms and storage areas, open and close doors, and tinker with lights and sound equipment. When cast and crew members discover their antics, they also hear the children laughing.
Two teams of psychic investigators, working independently of each other, both reported encounters with Isaac and Maria. They even called them by the same names. They also reported the same cause of death: a fire.