Stupidity: If the ninja can inhabit a dead body (and one that has been dead for a LONG time, even) without any penalty in his agility and powers and it is stated that only another ninja can truly kill him (which surely seems correct, since he would still fight even when hit by hundreds of bullets), the whole movie plot that involves him possessing Christie - who is a reluctant and part-time host - does not quite make sense.
Ninja III: The Domination (1984)
1 stupidity
Directed by: Sam Firstenberg
Starring: Lucinda Dickey, David Chung, Jordan Bennett
Continuity mistake: At the start of the film, Hanjuro intimidates a bodyguard by crushing a golf ball with his hand. In the initial shot, his palm faces outward. In the next shot, his palm faces inward. (00:03:55)
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Trivia: The scenes of Billy and Christie gawking at the final battle between the two ninjas were filmed months after principal photography. Lucinda Dickey is wearing a wig because she had already cut her hair short for her role in Breakin'.