Nightmare Fuel: Yin Yang Yo!
- In "Deja Foo", Yang has to watch Ultimoose burn Yin and Master Yo to death until they're ashes. They don't show much, but it's still a bit unnerving.
- Some of Yuck's twisted looking expressions (especially in "Yin Yang Yuck!") can get pretty creepy.
- The fact that the Nightmaster was able to commit mass genocide and possibly wouldn't refrain from doing it again.
- The Woo Foo Aura Drain is this, especially considering that a Woo Foo powered being losing their abilities is enough to kill them unless they find their parent: when Yin is hit with one of these by Eradicus, her eyes become entirely black and her body is frozen while her abilities are drained out of her.