Corrected entry: Ghosts don't crossover as long as they have unfinished business. Casper's father had invented a machine called the lazarus, in a quest to bring Casper back to life, but he never got it to work. Therefore, Casper's father should have stayed as a ghost until he succeeded.
mightymick
2nd Aug 2010
Casper (1995)
24th Jul 2010
Casper (1995)
Corrected entry: It is said that ghosts don't crossover as long as they have unfinished business. This means Casper, Stretch, Fatso and Stinky should have unfinished business, but why they are present is never explained.
Correction: I don't see how this could be considered a plot hole. It's just an element that they decided to ignore. The story is about the misadventures of a friendly ghost and some annoying ghosts. Why they're there really doesn't play a part in the theme of the movie.
That still doesn't answer the question as to what their unfinished business is which they have seen as how they haven't crossed over.
Correction: No, ghosts who have unfinished business may choose to cross-over or choose to stay in the hopes of completing their business; they don't have to stay. Even so, Casper's father built the machine to bring his son back to life. Once he died, he'd no longer need his son to be alive in order to be with him again. That means he had no unfinished business.
Phixius ★
Not to mention it is from a newspaper that Casper's father was declared insane and presumably sent to a mental institution which were quite inhumane and horrifying at that time with their treatments. It's sad to think of, but quite possible the institution drove him to a point where he wasn't in a condition to care about coming back as a ghost to bring Casper back to life any longer.