* DawsonCasting: Averted; all of the teenagers are played by actors between the ages of 13 and 15; Casper's voice actor is 14 [[spoiler:with the actor portraying his briefly restored body just about pushing it at 17]].
* DeletedScene: In the mirror morph scene, Dr. Harvey was originally also going to get changed into Steven Spielberg. The cameo was actually filmed, but cut from the film for pacing reasons. Spielberg was actually very happy about this, feeling that he's not much of an actor and was quite nervous in front of the camera.
* HeyItsThatGuy:
** [[EverybodyLovesRaymond Robert Barone]], [[Film/IndependenceDay President Whitmore]], [[Creator/MontyPython and that funny British dude]]. Also in the first movie, [[spoiler:human Casper]] is portrayed by Devon Sawa, who would later portray [[FinalDestination Alex Browning.]]
** A then unknown [[LizzieMcGuire Hilary Duff]] playing Wendy in the third movie.
* MoneyDearBoy: The only explanation for the celebrity cameos. Or the long-term presence of Eric Idle.
** Clint Eastwood and Mel Gibson's cameos were technically done out of a favor to Steven Spielberg, though this probably played a part in it too.
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