Hamlet calls death "that undiscovered country from whose bourn no traveler returns."

But he's wrong. Some do return.

Each night after the applause dies, the curtain falls, the audience vanishes, the cleaners dust, and the lights are killed, great theatres become dark and silent places. But not always quite empty.

That's when the theatre ghosts make their entrance and strut and fret their hour upon the shadowed boards, illuminated only by the ghost light, the solitary lamp that is required to burn through the night on every Broadway stage.

Many of Broadway's busiest theatres continue to be just as busily haunted by spirits, some with well-known names and histories.

Good Morning, Olive (named for one of the most beautiful and temperamental of Broadway's ghosts) is about the ghosts that haunt theatres in New York and around the world.

Broadway is the playground of stars, so it's probably not surprising to learn that even its ghosts are stars. Meet some of Broadway's best known-and most active-celebrity ghosts. Don't worry: like Casper, they tend to be friendly. For the most part.