ADMIT IT, you were scared when the universe was destroyed. If you understood the Gainax Ending quickly enough for the repercussions to take you by surprise, that is.
Kingfin was kinda scary.
Also, right before Bouldergeist explodes, his uvula pulsates, his head shrinks, and his eyes triple in size... and he explodes...
The NPC bees are cute, but take a close-up look at their faces...
The Lumas' cycle of gorging themselves, and then committing suicide by exploding into a new celestial object. They are eventually being reborn somehow, but these guys are happy that they are exploding.
Bears a hilariously disturbing resemblance to a certain kinky fetish.
That gigantic Electric Jellyfish you first see above your head while trying to swim up and around it.
When your last point of health is taken away by electrical sources, Mario turns into a skeleton. That's right, he didn't just get hurt, he is completely and unmistakably dead.
This music was always creepy and strangely downbeat.
When Mario's hand rises up when he sinks in sand or toxic waste, all while hearing him drown.
When Mario touches dark matter, he slowly disintegrates, and his life bar isn't empty until AFTER Mario is completely gone. He feels the whole thing!
The warp sound effect that plays when floating to a star or another obstacle can be a little unnerving similar to example nine.