If Jeff and the others are in a Dark World of Creepypasta, why do they have illusion forms?
Presumably for when they go out into the human world. Jeff has to get his victims from somewhere, doesn't he?
None of the creepypastas have them change appearance when killing people, though, so it must just be for when he wants to go to a human store, or somewhere else in the human world, and doesn't want to draw attention to himself.