Tricksters are a type of ghost.
Tricksters are the most common ghost type encountered by the inexperienced ghostologist. Announcing that you are determined to undertake a scientific study of ghosts seems to cue a sudden rush of apparent hauntings that usually turn out to be just one or two tricksters. Not hard to outwit, tricksters can become a ghostologist's firm allies once they are convinced of your seriousness to understand them.