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Nightmare Fuel: The Megas
The fact that Dr. Light is singing I Want To Be The One To Watch You Die.
Afraid of the Dark is about Shadow Man consciously losing his former personality to darkness after Dr. Wily repairs and reprograms him—and he's terrified. At around 3 and a half minutes in, the darkness sings to him.
The Haystack Principle gets nightmarish when Needle Man starts singing about how much he loathes and fears his new body, while another voice repeatedly confirms that this is who he is.