Who Said Boo?

In the green, green castle with the green, green door
And green, green carpets on the green, green floor,
There lived a little ghost who was never seen,
And that is because he was green, green, green!
The naughty little ghost loves giving his unsuspecting victims a fright with a loud ‘Boo!’ they can’t see him, but the reader can! Each character blames the wrong person, until the clever jester finds an unexpected way to expose the culprit!