Nightmare Fuel / Pokémon Stadium

• The one-hit KO animations, particularly the ones for Horn Drill and Guillotine, especially when they connect.
• Jynx's fainting animation, in which it cries, suddenly freezes and its entire body disappears; that is except its hair, which simply drops on the ground. All of this gives the impression that it melted in the same manner as the Wicked Witch of the West.
• Misdreavus' fainting animation is similar: it blinks out of existence with a Tear Jerking look on its face, leaving its string of pearls, which falls to the ground and shatters.
• When Arceus or Giratina use Shadow Force. Especially Giratina.
• Jigglypuff's fainting animation. It deflates. However, it becomes a bit of a Nightmare Retardant as said fainting animation becomes one of its taunts in the Super Smash Bros. series, having it deflate willingly and become completely fine afterwards.
• Kangaskhan looks like she's choking when she faints.
• When Magnemite, Magneton, and Porygon faint, their entire bodies break apart. All three were updated in later games to simply fall over with "X" eyes.
• Abra's creepy spasms whenever it got knocked out.
• The Gym Leader Castle map in the first Pokémon Stadium. You have a path with 8 gym towers in a cavernous area◊ with smoke all around that seems to lead into a volcano that actively has smoke and lava pouring out of it. Then, when you beat the 8 Gyms, the smoke from the volcano reveals the Elite Four Castle built over the volcano.
• When you take a look on the Elite Four Castle map, you'll see a ghostly-looking Venusaur on the left of the path to the Elite Four Castle entrance. The creepy cavern/volcano vibe may be why the entire Gym Leader Castle in Pokémon Stadium 2 was made to be less scary in appearance.
• Certain Pokémon models have been known to be creepy, like Crobat's more defined facial features, and Venusaur's eyes going bloodshot whenever it attacks.