Nightmare Fuel / Kirby: Right Back at Ya!
We really didn't need to see that.

Surely such a bright and innocent show based on such a bright and innocent series couldn't have its moments, could it? Wrong!
  • The weekly monsters are primarily filled with this. Most are actively violent and willing to cause harm, and with some imagination, it's pretty much guaranteed to score some frights. For example..
    • WolfWrath. It's a fire-breathing wolflike creature with massive claws, which rampages through Dedede's castle and nearly kills Meta Knight. As it is, Meta Knight spends most of the episode under a paralyzing curse, with Sword and Blade disregarding what nearly were his final words in favor of trying to find a way of freeing him from said curse.
    • Kirisakin. An apelike creature with scythes for hands, and probably the only creature of the show to directly kill someone, complete with a Dead-Hand Shot.
    • Masher. A Killer Robot filled to the brim with so many weapons it's not even funny. It also returns a second time, this time even more dangerous. The latter episode opens with Knuckle Joe fighting a losing battle against Masher 2.0, and then waking up in the castle after a dream about his dead father, covered in bandages with Tiff and Kirby standing over him. He sports said bandages for the rest of the episode, with Tiff repeatedly telling him to stay in bed, but no option to actually do so because Masher 2.0 has found him.
    • Destroyer. A flying saucer-like monster that is more Mechanical Abomination than Masher could ever hope to be. It is enormous, dwarfing King Dedede's castle. It fires off swarms of homing missiles that tear down the entire castle, and absolutely nothing short of Crash Kirby or the Halberd's laser could hurt it. Its missiles were so powerful they could actually damage the Warp Star, putting Kirby in a temporary coma and essentially chipping a sliver off of his soul. And then Holy Nightmare Co. decides to send down a whole fleet to tear down all of Dreamland.
  • Dedede in the dub is a parody of George Bush, and a hilarious one at that, but in the original, his idiocy leads to active death threats, and attempts at murder (usually of children), nearly every episode. He also holds a Book Burning to cover up the fact that he doesn't know how to read. The more you look, the clearer it is that he's a bit more than a harmless buffoon who only holds the title of King because the Cappies let him.
  • Some of the deaths can get a little more violent than might be expected from a kids show. Examples are burning to death, getting slashed in half, eaten (though that one is to be expected to an extent, given that it is Kirby), launched into the sun, and disintegration, among others.
  • Scare Tactics. From the numerous horror movie references (including an homage to the shower scene from Psycho), the ghosts (like a plasma ghost that leaps at the camera, and a baby ghost with a seriously disturbed face) to a seemingly bleeding skull (it was red paint, but still) to that clock room, to a torture room (containing Dedede's apparent death, complete with more red paint blood) to the chaos of it all, and the fact that it's an elaborate death trap Haunted House that Nightmare sent over without anyone knowing initially. In the end the place burns down, thanks to a mishap with Fire Kirby.
  • Escargone. The episode is about Escargoon not being recognized by anyone at all, due to the demon beast known as Erasem entering his mind. The only way it can be driven out so that he can be remembered again is to essentially torture him until it leaves, though the Looney Tunes-esque silliness of the torture methods in question can leave you not quite knowing if you should be horrified or laughing. It's ripe with Paranoia Fuel, and the fact that the monster actually lives at the end only adds to that.
  • Escargoon Squad. Very similar to Scare Tactics, it features Escargoon attempting to get revenge. Such examples include a a torture room. Also, one lightning flash causes Dedede to go into a horrific state of distortion, almost to the point of being unrecognizable.
  • The Holy Nightmare/Nightmare Enterprises Theme from the original version is surprisingly terrifying and mysterious.
  • Nightmare himself really lives up to his name. Not only did he conquer countless planets, he also wiped out an entire resistance group (with Meta Knight being the Sole Survivor) and sent a meteor crashing into Pop Star. And since his only weakness was the Star Rod, he was completely unstoppable until Kirby arrived to do so. Even worse in the Japanese version, where he would always exist as long as there was darkness in people's hearts.
  • The very first scene in the series shows a flock of sheep being attacked and devoured by a giant octopus. It even shows their bones and skulls fall to the ground afterwards.
  • Mumbies are mummified assassins that go around killing star warriors in the night. Not helping was the fact that its Hypnotic Eyes makes you too sleepy to fight back. If it weren't for King Dedede's stupidity, Kirby might have been done for.
    • Professor Curio was behaving pretty creepily when he was digging up the Mumbies in the first place, thinking it was a good luck charm. His glowing green eyes don't help.
  • Tiff almost getting crushed by the Dedede Stone. Partly because it's one of the few times King Dedede actually attempts to murder her, which took a lot of people used to his usual antics by surprise. Including our heroes, as Kirby looks on with an "Oh, Crap!" Jaw Drop and Tuff covers his eyes as the monster tries to crush her.
  • The ending to the episode where Dedede has a cavity. Throughout the episode he summons a monster to get rid of the pain only for him to later ask Kirby to destroy it. The scene cuts to Dedede making a horrified and crying noises before he gets his cavity taken care of. The episode ends with Dedede passing out while Kirby, Tiff and Escargoon are watching it getting removed. It's a lot more disturbing in the English dub.
    Escargoon: His Majesty has had low points, but I don't think he's ever been this down in the mouth.
  • The first half of "Tooned Out" is dripping with Fridge Horror. A trio of Otaku nerds gain an unhealthy obsession with Tiff. They proceed to stalk her, record her voice without her consent or knowledge, and even take pictures of her while she sleeps.
    • It's even worse in the Japanese version with the nerds' finished product, where they not only did they give their version of Tiff breasts, but the Manipulative Editing is even worse, making it sound like Tiff is trying to seduce the viewer.
  • One of the last episodes, dubbed Frog Wild in the English version, has Devil Kirby. You wouldn't imagine innocent, little Kirby destroying almost the whole of Cappy Town with such glee, would you? Plus, his Nightmare Face! It's surprising 4Kids let this episode air.
  • The fact that Kirby is essentially a Child Soldier. It's said he's supposed to be a baby, and that he was woken up for active duty 200 years too early. Now add Meta Knight's reaction from the first episode when he sees him for the first time...
  • During the last episode, Cappy Town is destroyed. When Tiff, Tuff and Kirby try to gather all the cappies, they all coldly turn towards them. This is especially chilling because they were all nice towards Kirby in every prior episode.