"These cheerful little spirits - called "Boos" - are often seen dancing and playing close to where they died. Boos are widely believed to be children who died suddenly and horribly.
It is not known how a Boo gets its mask, nor why no two Boos wear the same one. Removing it is not advised, as this will anger them - and besides, what lies beneath the mask are the dead child's remains.
This particular Boo goes by the name of Jessica, and as you can see, someone has removed her mask. She is currently searching for it."