Jennifer Brannon, left, hands her daughters Jane, center, and
Anne, right, tickets for 'Peter and the Starcatcher' at New
World Stages. Andrew Spear for The Wall Street Journal  At a
recent performance of "Cinderella," the stepsister leaned in for
a kiss with the local revolutionary while the audience watched
in rapt silence. Then a lone, little voice rang out in the
theater.   Few interruptions on Broadway are welcomed. Sources
of condemnation include a child chattering endlessly to a
parent, the crackling of candy wrappers or smells from smuggled-
in food, or the flash of a cellphone as someone surreptitiously
texts.  All jolt actors and audiences out of a performance and,
in extreme cases, reinforce a sense of society's general
decline. But there is one kind of disruption that can actually
enhance an experience, some said: the spontaneous reaction of a
small child.  "I wish we had more eeeewwwws," said Greg
Hildreth, who plays Jean-Michel, the stepsister's love interest
in "Cinderella." "To get a genuine re