No ghosts exist in the world of Mask or Menace, with the exception of one location: the city of Jeopardy, Nevada. For the most part, the ghosts' demeanor is reticent and disturbed. More specific reactions would depend how Klaus approached them and what he had to say—if you app him, you're welcome to comment to the plotting post with more information on his attempts at communication, and we'll be glad to give you the relevant details!