How well does pop star Jessie J know her hit “Bang Bang”? So well that she can sing it with her mouth closed. Yes, you read that right. “I discovered when I was little that I could pretend I was in a box,” she revealed to Graham Norton during a visit to his talk show, demonstrated a form of ventriloquism that does indeed make her sound confined and muffled. “As I got older, I discovered that I could sing [the same way].” And then she does it, and it’s startlingly clear and really disturbing. Follow Ned Ehrbar on Twitter: @nedrick