Continuity mistake: When Dr. Harvey sees his dead wife, Amelia, for the first time as a ghost, he talks to her half way up the staircase in the manor while the party is going on. The camera changes angles a few times from the side of their heads, to Amelia's view of Dr. Harvey. In each different camera angle, his hair changes place, from the side of his head, it slips down in front of his face.
Casper (1995)
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Directed by: Brad Silberling
Starring: Bill Pullman, Christina Ricci, Eric Idle, Cathy Moriarty, Chauncey Leopardi, Malachi Pearson, Spencer Vrooman
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Kat: Drop dead.
Stretch: Too late.
Trivia: Early in the film, an SUV is smashed by a wrecking ball in front of Whipstaff. A real SUV was smashed for that film and it was obviously one that had been in a wreck previously. Notice that the passenger door is crooked and pulled away from the frame.
Answer: The Ghostly Trio were, at the time, playfully teasing James, so Fatso wearing something else instead of what Amelia was seen wearing in the photo, was just a way for them to have some fun at James' expense. At the end of the movie however, they did keep their promise and let James have one final chance to speak to his wife.
Why that specific outfit, though?
Again, to playfully tease James.